Sclerocoelus Marshall, 1995

Genus Sclerocoelus Marshall, 1995 View in CoL

Sclerocoelus Marshall, 1995: 283 View in CoL (masculine). Type species: Limosina sordipes Adams, 1904 View in CoL , original designation.

Sclerocoelus View in CoL – Marshall 1997: 97 [diagnosis, phylogeny, key, illustrations]. — Roháček et al. 2001: 248 [world catalog].

Diagnosis

Almost all Sclerocoelus species exhibit the following combination of characters: (1) very broad lunule; (2) very broad alula; (3) a proximal posterodorsal seta on the mid tibia; (4) well-developed postsutural intra-alar bristle; and (5) complex male genital pouch composed of several additional sclerites. Other diagnostic characters include (6) a midventral seta on the female mid tibia (absent in males) and (7) costa terminating at the end of R 4+5. Some species lack the proximal posterodorsal mid tibial seta ( S. mandibulum sp. nov. and S. argentinensis sp. nov.), however all other diagnostic characters are present in these species. One of the brachypterous species of Sclerocoelus ( S. aduncus sp. nov.) has a small alula but has all other diagnostic characters of the genus (the other brachypterous species have a very broad alula).

Sclerocoelus inornatus sp. nov. and S. lutosus sp. nov. lack the distinctively sclerotized male genital pouch that characterizes other Sclerocoelus species, but they do have the other defining characters of Sclerocoelus as listed above (with the possible exception of the dimorphic mid tibia in S. inornatus , as no females are known). A morphological phylogeny ( Fig. 2 View Fig ) suggests that the relatively simple genital pouch of these species represents a character reversal rather than a plesiomorphic trait, however neither species was available for sequencing.

Redescription

BODY. Colour yellow to dark brown. Length 1.8–5.3 mm.

HEAD. Brown, variable portion of frons orange; face, gena, and antennae orange to brown; frontal vitta, interfrontal plate and orbital plate subshining, indistinctly microtomentose. Frontal width 2.2–2.4 × frontal height. Two or three pairs of strong interfrontal bristles usually surmounting a very fine third or fourth pair; two strong lateroclinate orbital bristles, anterior orbital 0.4–0.7 × length of posterior; ocellar bristle large and diverging; postocellar bristle small; inner and outer vertical bristles large; inner and outer occipital bristles large. Vibrissa large, vibrissal angle with one subvibrissal seta; gena with an enlarged anteroventral seta and several smaller setae. Palpus yellow to brown, clavate, with two large preapical ventral setulae. Lunule usually broad, bulging and prominent, always broader in female than male; face slightly excavated and usually short, medially about 0.3–1.5× as tall as lunule, medial keel short and usually only slightly developed. Antennae divergent; pedicel with long marginal setae; postpedicel ovoid, somewhat flattened on outer surface; arista long-pubescent. Eye variable but usually large, greatest height 1.1–5.0× shortest genal height, posteroventral corner concave from broadened gena.

THORAX. Brown, scutum paler laterally. One or two (usually) distinct postsutural dorsocentral bristles, anterior pair sometimes reduced, 0.3–0.7 × length of posterior (prescutellar) pair, separated by 4–12 rows of acrostichal setulae. Two postpronotal bristles, outer bristle large and inner bristle small; two notopleural bristles, anterior slightly larger than posterior; two strong supra-alar bristles; postalar and intrapostalar bristles large; prescutellar acrostichal setulae usually enlarged (3.0–4.0 × length of anterior setulae). Prosternum linear, membrane around prosternum usually bare but sometimes with additional setulae-bearing sclerites. Katepisternum with a very fine anterior setula and a large posterior bristle. Scutellum subtriangular, 1.3× as wide as long, with four long marginal bristles in usual positions.

LEGS. Brown to yellow. Fore femur with 3–5 large ventral preapical setae. Dorsal surface of mid tibia with three (one small and one large anterior and one small posterior) proximal setae and three (one small and one large anterior and one large posterior) distal setae except in male S. mandibulum sp. nov. Ventral surface of male mid tibia with an apicoventral bristle and two rows of stout setae in apical quarter to two-thirds, mid femur with two corresponding rows of stout proximal setae; ventral surface of female mid tibia with strong midventral bristle and long apicoventral bristle. Mid basitarsus with distinctly enlarged basal ventral setula. Hind tibia with stout apicoventral seta.

WING. Hyaline to infuscate. CS2 0.6–1.0 × CS3. R 2+3 sinuate, basal curve almost straight and distal curve strong; R 4+5 slightly sinuate, ending just before wing tip; costa ending at or extending just beyond end of R 4+5 (1–3× costal width). M 1 extending to wing tip as distinct sinuate crease. M 4 extending past dm-m 1.1–1.3 × length of dm-m. CuA+CuP sinuate, almost reaching wing margin. Alula almost always large, ovoid. Halter pale brown to brown.

MALE ABDOMEN. Dark brown, posterior edges of tergites usually slightly desclerotized. T2–5 and S2–4 long-setose with large posterolateral setae. S5 highly variable, usually rectangular; posteromedial chaetotaxy variable. Genital pouch including multiple sclerites, most of which seem to be derived from the ventral part of S6+7 (sclerites A–E, as defined in Materials and Methods). Epandrium variable, usually wedge-shaped, and uniformly long-setose; perianal pads usually weakly developed and membranous, but sometimes sclerotized and enlarged. Cercus usually weakly differentiated from epandrium, usually widely separated but sometimes entirely or partially fused medially to form subanal plate; pseudocercus usually small and separated from epandrium, sometimes fused to inner ventral corners of epandrium or entirely absent; when present, almost always with three setae. Halves of subepandrial sclerite usually strongly arched and joined medially. Subcercus usually large and complex. Hypandrium usually large; anteromedial hypandrial apodeme elongate but usually shorter than phallapodeme; lateral hypandrial arm strongly arched, separate from anteroventral corner of epandrium and usually separate from anteromedial hypandrial apodeme (fused to anteromedial apodeme in S. punensis sp. nov., S. paranebulosus sp. nov. and S. penai sp. nov.). Surstylus variable, usually larger than subcercus. Postgonite variable. Phallapodeme large, curved, sometimes dorsoventrally flattened apically; basiphallus variable, often stout with a neck-like distal part, epiphallus variably developed; distiphallus usually small, largely membranous, and supported by numerous sinuate sclerites.

FEMALE ABDOMEN. Dark brown, edges of preabdominal sclerites, especially sternites, usually desclerotized. T2–6 and S2–6 uniformly long-setose with longer posterolateral setae. T7 broad, rectangular; T8 either desclerotized dorsomedially, appearing as two large lateral sclerites, or divided into pale dorsal sclerite and two dark lateral sclerites, posteromedial corners of lateral sclerites usually expanded posteriorly. Epiproct usually large, shield-like and often desclerotized along midline, appearing as two separate sclerites, usually densely setulose, almost always with pair of large dorsal setae. Cercus variable, usually elongate, always densely setulose, usually with large apical and dorsal setae. S7 broad, often pointed posteromedially, long-setose with 4–6 distinctly enlarged, preapical, posterior setae; S8 usually highly reduced, often divided into two small, lateral sclerites each with two minute sensory setulae, though sometimes with only a single large, medial sclerite or entirely membranous/absent. Hypoproct large, broad, U-shaped, densely setulose posteriorly with 5–16 distinct setae. Three or (rarely) two spermathecae, bulb various, sometimes spherical or cylindrical but asymmetrically bean-shaped in one major clade, often with 1–2 invaginations, invaginations sometimes with a finger-like, central process pointing outwards; paired spermathecae (when present) smaller than single spermatheca; ducts short.

Similar and related genera

Marshall & Dong (2008) noted superficial similarities between the widespread southern hemisphere genus Parasclerocoelus and some species of Sclerocoelus , including a large intra-alar bristle, sinuate R 2+3, almost straight R 4+5, a double row of stout setae on the apicoventral surface of the mid tibia, large S6–8, pruinose thorax and similar female terminalia. However, Parasclerocoelus has a narrow alula, a small lunule and no posterior proximal seta on the mid tibia. Its male genital pouch includes an arm of S6 that extends across the anterior face of the genital pouch but lacks the multiple genital pouch sclerites that define Sclerocoelus .

The only species of the high Andean genus Paramosina is also externally similar to sympatric species of Sclerocoelus . Marshall & Yau (2014) noted the broad lunule and broad alula as similarities, but noted the simple male genital pouch, complete subanal plate, well-developed cerci and epiproct in the female as significant differences between the two genera. The male S6 is divided into two ventral lobes in Paramosina , but it does not break into separate pieces ventrally as in Sclerocoelus . Paramosina also differs from Sclerocoelus in lacking the posterior proximal seta on the mid tibia in both sexes and in lacking the midventral mid tibial bristle in females. Nine species of Sclerocoelus were collected along with the type series of Paramosina hirsuta Marshall, 2014 at 3600 m a.s.l. (Quebrada Mishahuaycu, Ecuador).

Males of the small African genus Parapoecilosomella Papp, 2008 have a large genital pouch superficially similar to some Sclerocoelus , but the two species of Parapoecilosomella differ so widely from Sclerocoelus in wing venation and other features it seems unlikely that there is a close relationship.

Marshall (2000) suggested Sclerocoelus as a possible sister group to the mostly Neotropical genus Chespiritos , with which it shares a broad lunule and well-developed intra-alar bristles. Kuwahara & Marshall (2020) pointed out further similarities between the basal species of Chespiritos and Sclerocoelus species in the S. galapagensis species group. Sclerocoelus can be easily distinguished from Chespiritos by the broad alula, four scutellar bristles, single proximal posterodorsal seta on the mid tibia, male mid tibia without a midventral bristle, costa ending near the tip of the wing at its junction with R 4+5, and complex genital pouch.

Phylogeny

Phylogenetic trees were generated from the matrix using TNT with New Technology search (sectorial search and tree-fusing). Analysis of the entire character state matrix ( Table 1 View Table 1 ) yielded four equally parsimonious trees (length = 196, consistency index = 0.20, retention index 0.69). The preferred tree ( Fig. 2 View Fig ) places the very similar species S. flavus sp. nov. and S. meridensis sp. nov. as sister species. Four distinctive branches of this tree are here treated as named species groups: the S. dasysternum species group, the S. galapagensis species group, the S. regularis species group, and the S. sordipes species group. Seven relatively plesiomorphic species are treated as ‘basal lineages’, and 22 other species are not placed in named species groups.

The S. dasysternum species group ( S. costaricensis sp. nov., S. dasysternum sp. nov., S. grandicercus sp. nov., S. latibarbus sp. nov., S. masneri sp. nov., S. nitidistylus sp. nov., S. ocellatus sp. nov., S. recurvatus sp. nov., S. rostrum sp. nov., S. synorios sp. nov., and S. vulgatus sp. nov.) is characterized by a dense, rectangular patch of posteromedial setulae on the male S5, relatively short surstyli, and usually large sclerite F. Most species in the S. dasysternum species group have male S5 asymmetrically developed (reduced on the left or right posterior corners, sometimes both). This group is largely Central American though S. masneri is known only from Venezuela, S. synorios ranges into the United States, and the range of S. vulgatus extends to Peru.

The S. galapagensis species group ( S. andensis Marshall, 1997 , S. binus sp. nov., S. brasilensis Marshall, 1997 , S. caligarius sp. nov., S. caribensis Marshall, 1997 , S. copiosus sp. nov., S. elephas sp. nov., S. galapagensis Marshall, 1997 , S. hemorrhoidalis Marshall, 1997 , S. subbrevipennis ( Frey, 1954) , and S. tantus sp. nov.) is characterized by the presence of additional sclerites in the membrane beside the prosternum. A smaller clade within the S. galapagensis species group is characterized by an elephant trunk-like epiphallus on the basiphallus. The S. galapagensis species group is the most widespread species group ( Mexico to northern Argentina and throughout the Caribbean), and includes the only unequivocal Sclerocoelus species with a distribution outside of the New World ( Tristan da Cunha).

The S. regularis species group ( S. dominicensis sp. nov., S. irregularis sp. nov., S. pararegularis sp. nov., S. regularis ( Malloch, 1914) , and S. turpis sp. nov.) is characterized by a relatively small body size (1.8–3.1 mm), yellow legs, large, mitt-shaped surstyli (height 2.0× length), and flattened, shield-like subcerci. The S. regularis species group occurs from Mexico south to northern Argentina, with one species ( S. dominicensis ) known only from Dominica.

The S. sordipes species group is a small group made up of two of the three Nearctic species of Sclerocoelus , the very similar S. sordipes ( Adams, 1904) and S. parasordipes sp. nov. This group is recognized by a characteristically pigmented male S5 with a large setulose medial patch.

CO1 sequence analyses (barcode trees)

Results

Figures 3 View Fig and 4 View Fig show the NJ and ML trees, respectively, for the CO1 dataset including Sclerocoelus , Parasclerocoelus , Chespiritos , and Archiceropter a. On the NJ tree, but not the ML tree, Parasclerocoelus comes out within Sclerocoelus , where it is recovered in the same branch as some of the relatively plesiomorphic Sclerocoelus species. Three of the four named Sclerocoelus species groups recognized in the morphological analysis ( S. dasysternum , S. sordipes , and S. regularis species groups) were recovered as single branches in both trees. The S. galapagensis species group, however, was recovered in two places in both trees, suggesting that the species newly added to the group herein might render it a paraphyletic group: S. andensis , S. caribensis and S. brasilensis come out as closer to the S. regularis group than to the newly described species S. elephas sp. nov. and S. copiosus sp. nov. on the ML tree, but on the NJ tree S. elephas and S. copiosus are closer to the S. regularis group. Sclerocoelus binus sp. nov. is next to the latter two species on the NJ tree but next to S. andensis , S. caribensis and S. brasilensis on the ML tree.

Discussion

The compelling morphological synapomorphies for Sclerocoelus suggest that it is monophyletic, but if the NJ tree topology is correct then the two ‘S clerocoelus ’ branches recognized on that tree would instead be a broadly defined Parasclerocoelus (including the species here treated as unplaced or plesiomorphic Sclerocoelus ) and a more narrowly defined Sclerocoelus including all previously named Sclerocoelus species and the four named species groups of Sclerocoelus . Similarly, the S. galapagensis group is readily recognizable on the basis of morphological characters and the definition of the group remains unchanged despite the conflicting CO1 trees.

The most interesting apparent conflict between the morphological and molecular trees is the consistent division of the genus into two separate branches in the molecular trees, in contrast to the morphological tree that identifies a paraphyletic series of ‘basal lineages’ associated with very high elevations or temperate latitudes. Both the ML and NJ trees recover one branch with both of the putatively basal species sequenced and also including most of the sequenced species currently unplaced to species group (and, in the case of the NJ tree, also including Parasclerocoelus ). The morphological and molecular trees thus represent two different competing hypotheses about the history of the group, one positing a south temperate/high Andean origin with successive speciation events in extreme environments prior to the origin of a single large clade now most diverse in cloud forests, the other involving an early division of the genus into a single high Andean/southern South American clade and a second clade with a more northern distribution.

The CO1 analyses may benefit from additional taxon sampling ( Heath et al. 2008) as only 25 of the 58 species considered here are included in the molecular tree. The findings may also be a result of a poor phylogenetic signal strength in CO1 barcode region compared with other genes ( Ekrem et al. 2010; Maddison et al. 2014), but the availability of CO1 data and ease in getting additional material sequenced provided us an opportunity to compare the data with the main morphological study. Some studies in acalyptrate Diptera have found CO1 contains some measure of phylogenetic signal by itself (e.g., Lindsay & Marshall 2023) but many studies have found that CO1 is best used in conjunction with other genes (e.g., Winkler et al. 2009; Ekrem et al. 2010; Kekkonen et al. 2015; Han & Ro 2016). This study’s development of the Sclerocoelus CO 1 dataset will aid future multi-gene studies in examining the relationships both within Sclerocoelus and with other Limosininae genera.

Biology

Larval Sclerocoelus remain unknown, but several specimens of S. copiosus sp. nov. and S. nitidistylus sp. nov., emerged from a refuse pile under an Eciton burchellii Westwood, 1842 bivouac in Costa Rica, and a number of Sclerocoelus species have been found in or near nests of leafcutter ants and army ants. The common and very widespread species Sclerocoelus copiosus was the most numerous sphaerocerid in and around the aforementioned Eciton burchellii midden in Costa Rica, with 24 specimens collected, but nine specimens of S. nitidistylus and a single S. vulgatus sp. nov. were also collected in or around the refuse pile (along with about 20 Leptocera hexadike Buck, 2009 , some Pterogramma Spuler, 1924 , and a few Boreantrops talamanca Kits & Marshall, 2015 ). Other possibly ant-associated Sclerocoelus species include S. costaricensis sp. nov., which we have swept over nests of Atta Fabricius, 1805 , swept over columns of Eciton Latreille, 1804 and collected in raised emergence traps over Atta nests; S. vulgatus , which we have swept over Atta nests and swept over Eciton raids; and S. caribensis Marshall, 1997 which we have swept over Atta nests.

Although most of the specimens examined are from cloud forests between 1500 and 2000 m a.s.l., collecting records for the relatively plesiomorphic species are almost all high Andean, mostly from 2900 m a.s.l. or above and in many cases only from alpine habitats at 3500 m a.s.l. or higher.

Distribution

Sclerocoelus species occur from southern Canada (49°54′ N) to central Chile (32°51′ S), and throughout the Caribbean. The only definite Sclerocoelus species known from outside of the New World is S. subbrevipennis , apparently endemic to Tristan da Cunha. Sclerocoelus clarae ( Papp, 1973) , from Mongolia, is almost certainly misplaced in Sclerocoelus and is excluded from the species key below (see discussion below under species incertae sedis).

Ecuador, with 25 Sclerocoelus species including eight apparent endemics, appears to be a center of diversity for the genus, as are Venezuela (19 species, five endemic), Costa Rica (18 species, four endemic), Bolivia (18 species, three endemic), and Peru (14 species, none known to be endemic). These numbers, however, correspond closely to directed collecting efforts in appropriate habitats in those countries. The high diversity in Ecuador undoubtedly reflects the rich fauna and habitat diversity of the country, but it also reflects the second author’s extensive collecting efforts there as well as our long-term collaboration with Ecuadorian colleagues. On the other hand, the apparent low diversity of some South American countries is certainly an artefact, in part caused by the difficulty of obtaining permits and other obstacles to fieldwork in those countries. We are confident that many species of Sclerocoelus remain to be discovered throughout the neotropics.

Most species of Sclerocoelus are known from only one to three countries, but seven species are known from more than six countries ( S. caribensis from 15, S. rectangularis and S. vulgatus sp. nov. from eight, and S. brasilensis , S. copiosus sp. nov., S. regularis , and S. tantus sp. nov. from seven). Several species are known from the same collection events. For example, Volcán Tenorio ( Costa Rica) 2000, Monteverde Biological Reserve ( Costa Rica) 1986 and 2000, Tapantí National Park ( Costa Rica) 1999, Baeza ( Ecuador) 1987, near Tandayapa ( Ecuador) 1999, trout farm ‘San José’ (Nanegalito, Ecuador) 1999, Cock-of-the-Rock Lodge ( Peru) 2006 and 2007, Laguna de Lucerdo ( Venezuela) 1995, and Henri Pittier National Park ( Venezuela) 1994 each yielded more than four species per collection event. Nine species are known only from the second author’s collections.

The morphological phylogeny suggests that the origin of the genus was in the high Andes of southern South America with multiple speciation events in South American alpine environments before part of the genus apparently split into derived clades. One of the derived clades is characteristic of forested habitats in Mexico, the Caribbean or Central America and one is associated mostly with South American cloud forests. The latter clade also includes species from the Galapagos and Tristan da Cunha and the former includes a pair of North American species and one species found in Mexico and North America. A few species in each of the larger derived species groups have widespread Neotropical-Caribbean distributions. Sclerocoelus vulgatus sp. nov., for example, is a member of the mostly Central American clade but ranges from Mexico and Central America south to Peru. Sclerocoelus copiosus sp. nov., a commonly collected member of the South American cloud forest clade, is found from Bolivia north to Costa Rica. Most of the Mesoamerican and Central American species belong to the S. dasysternum group, although the more plesiomorphic S. regularis group also includes Mexican, Caribbean and widespread Central American species. The S. galapagensis group sensu Marshall (1997) now includes several South American cloud forest species as well as species from the Galapagos and Tristan da Cunha. The S. sordipes group, comprising just two Nearctic species, is weakly supported as the sister group to the S. galapagensis group.

Key to the species of Sclerocoelus View in CoL

The following three letter country codes are used in the key: ARG ( Argentina), BLZ ( Belize), BOL ( Bolivia), BRA ( Brazil), CAN ( Canada), CHL ( Chile), CRI ( Costa Rica), CUB ( Cuba), DMA ( Dominica), DOM ( Dominican Republic), ECU ( Ecuador), GRD ( Grenada), GTM ( Guatemala), GUF ( French Guiana), GUY ( Guyana), HND ( Honduras), JAM ( Jamaica), KNA ( Saint Kitts & Nevis), LCA ( Saint Lucia), MEX ( Mexico), NIC ( Nicaragua), PAN ( Panama), PER ( Peru), PRI ( Puerto Rico), PRY ( Paraguay), SHN ( Saint Helena, Ascension & Tristan da Cunha), SLV ( El Salvador), TTO ( Trinidad and Tobago), USA ( United States of America), VEN ( Venezuela).

1. Brachypterous species (as in Fig. 11A View Fig ) with wing never extending past posterior margin of T4. Cerci fused basally to form subanal plate and projecting ventrally but not divided to form separate subcercus (as in Fig. 11B View Fig ). Surstylus broad, mitt-like ( Figs 11C View Fig , 55C View Fig , 75C View Fig , 90C View Fig )........................... 2

– Macropterous species (as in Fig. 1A View Fig ) with wing fully developed, extending past apex of abdomen. Cercus and surstylus of various forms............................................................................................... 5

2. Interfrontal bristles in three large pairs surmounting a fourth smaller pair. Mid tibia with five dorsal setae in distal half .............................................................................................................................. 3

– Interfrontal bristles in two large pairs surmounting a third smaller pair. Mid tibia with 2–3 dorsal setae in distal half .............................................................................................................................. 4

3. Head and legs yellow. Male S5 with dense patches of setae flanking posteromedial desclerotized area ( Fig. 56B View Fig ). Subcercus short, less than half length of surstylus ( Fig. 55D View Fig ). Postgonite curved and evenly tapered............................................................................................... S. flavus sp. nov. (VEN)

– Head and legs brown. Male S5 with only scattered setae flanking dark posteromedial lobe ( Fig. 91B View Fig ). Subcercus elongate, at least half length of surstylus ( Fig. 90B View Fig ). Postgonite sinuate and almost parallel-sided......................................................................................... S. meridensis sp. nov. (VEN)

4. Eye height 3.0× genal height. Male S5 with a single row of stout setae along posterior margin, interrupted by posteromedial lobe ( Fig. 76B View Fig ). Ventral process of cercus with a posterior bulge about midlength ( Fig. 75C View Fig ). Postgonite broad basally, narrow at apex........ S. limbus sp. nov. (BOL, PER)

– Eye height 5.0 × genal height. Male S5 with setae mostly restricted to posteromedial emargination ( Fig. 12B View Fig ). Ventral process of cercus smoothly concave, without a prominent posterior bulge ( Fig. 11C View Fig ). Postgonite almost uniform in width ....................................... S. aduncus sp. nov. (ECU)

5. Interfrontal bristles in two large pairs and a third smaller pair.......................................................... 6

– Interfrontal bristles in three large pairs with or without a fourth smaller pair................................. 13

6. Two pairs of postsutural dorsocentral bristles, anterior pair large, distinct from surrounding acrostichal setulae.............................................................................................................................. 7

– Anterior postsutural dorsocentral bristle not distinct from surrounding acrostichal setulae, thus apparently only one (prescutellar) dorsocentral pair ....................................................................... 10

7. Legs yellow to pale brown. Male S5 with a dark posteromedial patch of dense setae ( Figs 43B View Fig , 97B View Fig ) .................................................................................................................................................. 8

– Legs dark brown. Male S5 uniformly setose or with a posteromedial row of slightly thickened setae, without a dense posteromedial patch ( Figs 54B View Fig , 73B View Fig ) ...................................................................... 9

8. Eye height 3.5× genal height. Male S5 with a medial patch of thick setae above dark, posteromedial patch of setulae ( Fig. 43B View Fig ). Outer surface of surstylus densely setulose ( Fig. 42C View Fig ). Female hypoproct large and deeply cleft anteromedially ( Fig. 44B View Fig ) ................................................................................ ................................................................... S. dasysternum sp. nov. (CRI, GTM, HND, PAN, TTO)

– Eye height 5.0× genal height. Male S5 with only an elongate, dark, posteromedial patch of setulae ( Fig. 97B View Fig ). Outer surface of surstylus bare ( Fig. 96C View Fig ). Female hypoproct small and deeply cleft posteromedially ( Fig. 98B View Fig )........................................................... S. nitidistylus sp. nov. (CRI, PAN)

9. Male S5 uniformly setose in posterior two-thirds. Genital pouch ( Fig. 54B View Fig ) sclerite A elongate, densely setulose, and partially separated from S6+7; sclerite F large, with its posterior apex sharply bent to the left. Subcercus strongly curved posteriorly, simple, blade-like ( Fig. 53B–C View Fig ). Surstylus short, bilobed ventrally. Postgonite evenly tapered .................................. S. espeletia sp. nov. (VEN)

– Male S5 with setae restricted to a posteromedial row and the right side. Genital pouch ( Fig. 73B View Fig ) sclerite A small, rounded, and not separated from S6+7; sclerite F small and simple. Subcercus gently curved anteriorly, wedge-shaped with a small, preapical, posterior lobe ( Fig. 72B–C View Fig ). Surstylus stout, subtriangular. Postgonite apically expanded and truncate...... S. lazulita sp. nov. (BOL, ECU, VEN)

10. Eye height 3.5× genal height; gena and face dark brown, contrasting with orange antennae. CS2 subequal to CS3. Male S5 with a narrow, T-shaped, largely bare, posteromedial lobe ( Fig. 148B View Fig ). Subcercus with a membranous ventral part ( Fig. 149C View Fig ). Female S7 pointed posteriorly; halves of S8 triangular................................................................ S. xynos sp. nov. (ARG, BOL, ECU, PER, VEN)

– Eye height 4.5× genal height; gena and face similar in colour to antennae. CS2 shorter than (0.7– 0.9 ×) CS3. Male S5 with a dark posteromedial patch of dense setae (as in Fig. 38B View Fig ). Subcercus various, but never with a membranous ventral part. Female S7 rounded or truncate posteriorly; halves of S8 subquadrate or rounded................................................................................................11

11. Gena dark brown. Male mid tibia with double row of ventral setae in apical half. Genital pouch ( Fig. 88B View Fig ) sclerite A rounded and bulging, with dense setulae. Pseudocercus small and separated from epandrium ( Fig. 87B View Fig ). Surstylus ventrally concave. Posteroventral corner of female T8 rounded ...................................................................................................... S. masneri sp. nov. (VEN)

– Gena orange-brown. Male mid tibia with double row of ventral setae in apical third at most. Genital pouch ( Figs 38B View Fig , 62B View Fig ) sclerite A elongate and bare (without setulae). Pseudocercus large, flattened, and fused to epandrium ( Figs 37B View Fig , 61B View Fig ). Surstylus ventrally convex. Posteroventral corner of female T8 pointed ...................................................................................................................................... 12

12. Large species (3.3–4.6 mm). Male S5 with an elongate (1.8–1.9× longer than wide) posteromedial patch of dense setulae, anterior margin of S5 straight ( Fig. 62B View Fig ). Postgonite broadly expanded and rounded apically. Female S7 widely desclerotized posteriorly; halves of S8 well separated ( Fig. 63B View Fig ); spermathecae spherical ( Fig. 63D View Fig ) ..................................................... S. grandicercus sp. nov. (CRI)

– Small species (1.9–2.6 mm). Male S5 with a stout (1.4× wider than long) posteromedial patch of dense setulae, anterior margin of S5 deeply excised ( Fig. 38B View Fig ). Postgonite almost parallel-sided and gently tapered apically.Female S7well-sclerotized posteriorly; halves of S8connected by a desclerotized band ( Fig. 39B View Fig ); spermathecae asymmetrically bean-shaped ( Fig. 39D View Fig ) .. S. costaricensis sp. nov. (CRI)

13. Membrane beside prosternum with 1–5 sclerites, each bearing one or more setulae...................... 14

– Membrane beside prosternum bare, without sclerites, or with a dark, semi-sclerotized, non-setulose patch (some S. rectangularis and S. chilensis , see couplet 24)........................................................ 22

14. Anterior (postsutural) dorsocentral bristle small, not distinct from surrounding acrostichal setulae ............................................................................................................................................. 15

– Anterior dorsocentral bristle at least 0.4× length of posterior seta and distinct from surrounding acrostichal setulae............................................................................................................................ 19

15. Eye height 5.0× genal height........................................................................................................... 16

– Eye height 3.0–3.5 × genal height.................................................................................................... 17

16. Acrostichal setulae in 7–8 rows between anterior dorsocentral bristles. Male S5 3.0× length of S4, largely bare except for a large, dark, densely setulose posteromedial patch flanked by desclerotized areas ( Fig. 51B View Fig ). Surstylus emarginate ventrally with a sinuate, tapered anterobasal inner lobe and two very thick, sinuate, ventral inner setae ( Fig. 50B View Fig ). Basiphallus with an elongate, curved, trunk-like epiphallus. Female epiproct setulose only medially; cercal setae elongate and sinuate ..................................................................................... S. elephas sp. nov. (BOL, ECU, VEN)

– Acrostichal setulae in 9–10 rows between anterior dorsocentral bristles. Male S5 1.0 × length of S4, densely setose laterally with a pair of very long setae flanking a small posteromedial lobe ( Fig. 24B View Fig ). Surstylus with a constriction in apical third, dividing it into a large basal section and a small apical section ( Fig. 23C View Fig ); basal section densely setulose on outer surface, apical section with several large inner setae. Basiphallus simple, without epiphallus. Female epiproct entirely setulose; cercal setae stout and straight...................................................... S. binus sp. nov. (BOL, CRI, ECU, PER, VEN)

17. Wing hyaline. Acrostichal setulae in 9–10 rows between anterior dorsocentral bristles. Head dark brown, with very little to no orange........................................................ S. caligarius sp. nov. (BOL)

– Wing at least slightly infuscate. Acrostichal setulae in 7–8 rows between anterior dorsocentral bristles. Head paler, at least gena and face orange to orange-brown............................................... 18

18. Fore femur with 5–6 enlarged ventral setae; male mid tibia with double row of ventral setae in apical fifth. Male S5 posteromedially emarginate with rows of marginal setae (cf. Marshall 1997: fig. 34). Posterior third of epandrium smooth, without transverse groove (cf. Marshall 1997: fig. 37); perianal pads strongly developed. Female epiproct with only four setae; S8 with two prominent, dark, posterolateral processes ............... S. galapagensis Marshall, 1997 (ECU – Galapagos Islands)

– Forefemurwiththreeenlargedventralsetae;malemidtibiawithdoublerowofventralsetaeinapicalthird. Male S5 with a dark, trapezoidal, densely setulose, posteromedial patch flanked by desclerotized areas ( Fig. 137B View Fig ). Epandrium with a transverse groove in posterior third ( Fig. 136C View Fig ); perianal pads bulging slightly but weakly developed. Female epiproct entirely setulose with two larger setae; S8 reduced to a pair of minute lateral sclerites ... S. tantus sp. nov. (ARG, BOL, BRA, ECU, PER, PRY, VEN)

19. Male S6+7 broken into small, dark sclerites posterior to S5. Perianal pad with a narrowed ventral part articulating with posterior arm of outer part of subcercus (cf. Marshall 1997: fig. 14). Posteroventral epandrial seta shorter than epandrium. Female S8 strongly differentiated into almost vertical lateral parts and concave ventral part ............................................................................................................ ........................................ S. brasilensis Marshall, 1997 (BOL, BRA, CRI, ECU, GUF, PAN, PER)

– Pocket-like genital pouch well developed and S5 sometimes with two dark, posteromedial lobes, but no small, separate, dark sclerites behind posteromedial part of S5. Perianal pads broad ventrally. Posteroventral epandrial seta longer than epandrium. Female S8 relatively simple, without prominent lateral parts....................................................................................................................................... 20

20. Two prominent, bare, dark lobes arising behind posteromedial part of male S5 (cf. Marshall 1997: fig. 2). Posterior arm of surstylus with relatively small bristles .......................................................... .............................................................. S. andensis Marshall, 1997 (ARG, BOL, ECU, PER, VEN)

– Area behind posteromedial part of male S5 simple (cf. Marshall 1997: figs 24, 46). Posterior arm of surstylus with 3–6 prominent, short, stout setae.............................................................................. 21

21. Acrostichal setulae in 7–8 rows between anterior dorsocentral bristles. Fore femur with 4–5 enlarged ventral setae. Male S5 short, shorter than genital pouch and 0.5 × length of S4, with posteromedial and posterolateral areas of long setae (cf. Marshall 1997: fig. 24). Genital pouch prominent, heavily sclerotized .......................................................................... S. caribensis Marshall, 1997 (CRI, CUB, DMA, DOM, ECU, GRD, GTM, GUY, HND, JAM, KNA, LCA, MEX, PER, PRI, SLV, VEN)

– Acrostichal setulae in 9–10 rows between anterior dorsocentral bristles. Fore femur with 7–8 enlarged ventral setae. Male S5 longer than genital pouch and 1.0× length of S4, with two setose posteromedial lobes, setosity of posterolateral area sparse (cf. Marshall 1997: fig. 46). Genital pouch well developed, but relatively small and lightly sclerotized.... S. hemorrhoidalis Marshall, 1997 (CRI, ECU, VEN)

22. Membrane around prosternum with dark, semi-sclerotized, non-setulose patches ......................... 23

– Membrane around prosternum entirely white and bare................................................................... 24

23. Distal half of mid tibia with three dorsal setae (two anterior, one posterior). CS2 0.7–0.8 × CS3. Male S5 with a very deep posteromedial cleft, lateral edges of which are flared outwards, setae largely restricted to a band about midlength and along posterior margin, anterior margin of S5 greatly expanded ( Fig. 120B View Fig ). Subcercus large, larger than surstylus, folded over itself ( Fig. 119B–C View Fig ) ....... ................... S. rectangularis ( Malloch, 1914) (CRI, DMA, DOM, GTM, HND, JAM, MEX, VEN)

– Distal half of mid tibia with two dorsal setae (one anterior, one posterior). CS2 1.0 × CS3. Male S5 very simple, posteromedially rounded slightly and uniformly setose in posterior half, anterior margin of S5 sinuate, left side moderately reduced ( Fig. 33B View Fig ). Subcercus smaller, subtriangular in posterior view and curved into a 90° bend in lateral view ( Fig. 32B–C View Fig ) ........................................... .................................................................................................................. S. chilensis sp. nov. (CHL)

24. Anterior pair of dorsocentral bristles small, indistinct from surrounding acrostichal setulae......... 25

– Anterior pair of dorsocentral bristles at least 0.4 × length of posterior pair, distinct from surrounding acrostichal setulae............................................................................................................................ 29

25. Mid tibia with only two anterodorsal setae in proximal half. Male S5 with a dark, asymmetrical, posteromedial cluster of short, thick setae ( Fig. 19B View Fig ); S6 with similar patch of setae anterior to a brush-like tuft on sclerite A. Subcercus very large and broad, almost as tall as epandrium and 1.5× as tall as surstylus ( Fig. 18B View Fig )............................................................ S. argentinensis sp. nov. (ARG)

– Mid tibia with a small posterodorsal seta in proximal half in addition to usual two anterodorsal setae. Male S5 various, but either with a large, dark, posteromedial patch of dense setulae or a dark, symmetrical, sclerotized patch with finer setulae. Subcercus various, but not more than 0.7 × as tall as epandrium or 1.2× as tall as surstylus; if close to 1.5× as tall as surstylus ( Fig. 144C View Fig ), subcercus flattened and triangular ................................................................................................................... 26

26. Interfrontal bristles in three pairs, middle pair largest and cruciate. Wing hyaline. Male S5 deeply and broadly emarginate posteromedially with a distinct, rounded posteromedial lobe and a dark, inverted Y-shaped posteromedial sclerite originating underneath(dorsal to)rounded lobe( Fig.110B View Fig ).Subcercus larger than surstylus, with a large, membranous, apical part ( Fig. 109C View Fig ) ..... S. penai sp. nov. (BOL)

– Interfrontal bristles in four pairs, first very small and others larger but subequal. Wing slightly infuscate. Male S5 various, either with a large, dark, posteromedial patch of dense setulae (as in Fig. 35B View Fig ) or with a pair of large, posteromedial setae surrounded by a setulose, desclerotized area ( Fig. 14B View Fig ). Subcercus smaller or equal to surstylus and entirely membranous, without a membranous apical part......................................................................................................................................... 27

27. Eye height 3.5× genal height. Fore femur with four enlarged ventral setae; distal half of mid tibia with two dorsal setae (one anterodorsal, one posterodorsal). Male S5 with a pair of large posteromedial setae surrounded by a setulose, desclerotized area ( Fig. 14B View Fig ). Female S7 strongly produced posteromedially into an apically emarginate process as long as main part ( Fig. 15B View Fig )........ ......................................................................................................... S. alpinus sp. nov. (ECU, VEN)

– Eye height 4.0 × genal height. Fore femur with three enlarged ventral setae; distal half of mid tibia with three dorsal setae (two anterodorsal, one posterodorsal). Male S5 with a large, dark, posteromedial patch of dense setulae ( Figs 35B View Fig , 145B View Fig ). Female S7 evenly rounded or produced posteromedially into a triangular process less than half as long as main part ( Figs 36B View Fig , 146B View Fig )............................... 28

28. Posteromedial patch of setulae on male S5 narrower, 1.9× as long as wide ( Fig. 35B View Fig ). Surstylus shorter than long, with a triangular, anterobasal inner lobe, outer surface brown. Posteroventral corners of female T8 strongly produced to points, female S7 pointed posteromedially............................... S. copiosus sp. nov. (BOL, BRA, CRI, ECU, PAN, PER, VEN)

– Posteromedial patch of setulae on male S5 wider, 1.4 ×as long as wide ( Fig.145B View Fig ). Surstylus taller than long, subtriangular, outer surface white. Posteroventral corners of female T8 more rounded, female S7 rounded posteromedially. S. vulgatus sp. nov. (CRI, GTM, HND, MEX, NIC, PAN, PER, TTO)

29. Eye height 1.1–2.7 × genal height.................................................................................................... 30

– Eye height 3.0–5.0 × genal height.................................................................................................... 38

30. Eye greatly reduced, 1.1–1.3 × genal height.............................................. S. ocellatus sp. nov. (CRI)

– Eye 2.0–2.7 × genal height............................................................................................................... 31

31. Anterior (postsutural) dorsocentral bristle large, 0.7× length of posterior (prescutellar) bristle. Wing hyaline. Male S5 with a long, dark, longitudinal, medial depression ( Fig. 115B View Fig ). Surstylus elongate, narrow, strongly sinuate with bifurcate apex ( Fig. 114C View Fig ) .............. S. punensis sp. nov. (BOL, PER)

– Anterior dorsocentral bristle distinct but smaller, 0.4–0.5 × length of posterior bristle. Wing slightly infuscate. Male S5 various, but never with a long, dark, longitudinal, medial depression. Surstylus various, usually broader, apex never bifurcate ................................................................................ 32

32. Legs and gena yellow. Male S5 with a large, ovoid, setulose posteromedial emargination extending almost to anterior margin ( Fig. 143B View Fig ). Cercus indistinct from epandrium; subcercus small, shield-like ( Fig. 142B View Fig ). Surstylus elongate but broad, 0.7 × height of epandrium, outer surface convex and inner surface concave ( Fig. 142C View Fig )................................................................ S. turpis sp. nov. (BRA)

– Legs and gena brown to dark brown. Male S5 various but never with a large, setulose posteromedial emargination.Cercus and subcercus various. Surstylus various but usually shorter than 0.5× epandrial height; if surstylus large ( S. dryadalis sp. nov.), male S5 without posteromedial emargination and cercus very large .............................................................................................................................. 33

33. Distal half of mid tibia with a small dorsal seta in addition to usual anterodorsal and posterodorsal setae. Male S5 wide, 3.5 × wider than long ( Fig. 48B View Fig )............................ S. dryadalis sp. nov. (VEN)

– Distal half of mid tibia with anterodorsal and posterodorsal setae only. Male S5 longer, 1.5–2.5 × wider than long ................................................................................................................................ 34

34. Distal half of mid tibia with two dorsal setae (one anterodorsal, one posterodorsal). Male S5 various but never with a dark, posteromedial patch of dense setulae .......................................................... 35

– Distal half of mid tibia with three dorsal setae (two anterodorsal, one posterodorsal). Male S5 with long setae largely restricted to lateral edges and a dark, posteromedial patch of dense setulae (as in Fig. 107B View Fig )....................................................................................................................................... 37

35. Epandrium boxy, with dorsal, lateral, and posterior surfaces at right angles to each other ( Fig. 40B– C View Fig ). Male S5 with very large and densely packed posteromedial patch of peg-like setae ( Fig. 41B View Fig ). Surstylus inverted U-shaped, with long anterior and posterior lobes ( Fig. 40C View Fig ) ................................ ............................................................................................................ S. cubus sp. nov. (ECU, PER)

– Epandrium saddle-shaped, dorsal, lateral, and posterior surfaces not at right angles to each other. Male S5 with scattered elongate setae not forming a dense posteromedial cluster ( Figs 59B View Fig , 65B View Fig ). Surstylus small and subquadrate...................................................................................................... 36

36. Fore femur with 4–5enlarged ventral setae.Eye height 2.0 ×genal height.Male S5deeply desclerotized posterolaterally, setae clustered along anterior edges of desclerotized areas, medially with a flattened V-shaped desclerotization ( Fig. 59B View Fig ). Additional sclerites of genital pouch very well developed. Postgonite elongate, 3.7 × as long as widest part ( Fig. 59A View Fig )............... S. frigidifrons sp. nov. (ECU)

– Fore femur with three enlarged ventral setae. Eye height 2.5× genal height. Male S5 extremely simple, rectangular, posterior margin unmodified, left side slightly extended posteriorly, uniformly setose in posterior two-thirds ( Fig. 65B View Fig ). Additional sclerites of genital pouch absent. Postgonite stout, 1.7× as long as widest part ( Fig. 65A View Fig ) ......................................... S. inornatus sp. nov. (ECU)

37. Male mid tibia with a double row of ventral setae in apical half. Acrostichal setulae in 6–7 rows between anterior dorsocentral bristles. Surstylus convex anterobasally (cf Marshall 1995: fig. 2). Lateral supporting sclerite of distiphallus uniformly thin (cf. Marshall 1995: fig. 5) ......................... ............................................................................................ S. sordipes ( Adams, 1904) (CAN, USA)

– Male mid tibia with a double row of ventral setae in apical third. Acrostichal setulae in 8–9 rows between anterior dorsocentral bristles. Surstylus concave anterobasally ( Fig. 106C View Fig ). Lateral supporting sclerite of distiphallus abruptly expanded apically ( Fig. 107A View Fig )........................................ ...................................................................................... S. parasordipes sp. nov. (CAN, MEX, USA)

38. Acrostichal setulae in 11–12 rows between anterior dorsocentral bristles.......................................... ................................................................. S. subbrevipennis ( Frey, 1954) (SHN – Tristan da Cunha)

– Acrostichal setulae in 4–9 rows between anterior dorsocentral bristles.......................................... 39

39. Legs yellow. Surstylus large, mitt-like, height 2.0× length (as in Fig. 125C View Fig ) ................................ 40

– Legs brown. Surstylus various, usually not large and mitt-like, at most height 1.7× length .......... 43

40. Medial patch of dense setulae on male S5 almost reaching anterior margin ( Fig. 126B View Fig ). Outer surface of surstylus largely bare, with only short, scattered setae ( Fig. 125C View Fig ); inner anterior ridge of surstylus with a deep notch ( Fig. 126D View Fig ).............................................................................................. ........................................... S. regularis ( Malloch, 1914) (BLZ, CRI, HND, PAN, SLV, TTO, VEN)

– Medial patch of dense setulae on male S5 well separated from anterior margin (0.3× length) (as in Fig. 105B View Fig ). Outer surface of surstylus densely long-setose (as in Fig. 104C View Fig ); inner ridge of surstylus entire ................................................................................................................................................ 41

41. Subcercus truncate apically ( Fig. 45B View Fig )............................................ S. dominicensis sp. nov. (DMA)

– Subcercus pointed or rounded apically ( Figs 66B View Fig , 104B View Fig )............................................................... 42

42. Postgonite sinuate ( Fig. 67A View Fig ). Subcercus rounded apically ( Fig. 66B View Fig ) .............................................. .............................................................. S. irregularis sp. nov. (ARG, BOL, BRA, CRI, ECU, PRY)

– Postgonite straight ( Fig. 105A View Fig ). Subcercus produced inwards apically ( Fig. 104B View Fig ) .......................... ......................................................................................................... S. pararegularis sp. nov. ( MEX)

43. Anterior dorsocentral bristle very large, 0.8× length of posterior pair. Genital pouch sclerites reduced, only sclerite G distinguishable ( Fig. 82B View Fig ) .......................... S. lutosus sp. nov. (BOL, PER)

– Anterior dorsocentral bristle smaller, 0.4–0.6 × length of posterior pair. Genital pouch sclerites well developed, with most pouch sclerites distinguishable..................................................................... 44

44. Distal half of mid tibia with two dorsal setae (one anterodorsal, one posterodorsal) ..................... 45

– Distal half of mid tibia with three dorsal setae (two anterodorsal, one posterodorsal) ................... 46

45. Gena bicoloured: orange anteriorly, brown posteriorly; face yellow. CS2 1.0 × CS3. Posterior margin of male S5 desclerotized with short, thickened setae ( Fig. 129B View Fig ). Surstylus subtriangular with a triangular, inner, anterobasal lobe and dense setae apically ( Fig. 128B–C View Fig )........................................ ................................................................................................................... S. riparius sp. nov. (ECU)

– Gena entirely orange-brown; face orange-brown; CS2 0.7–0.8× CS3. Posteromedial margin of S5 produced posteriorly with thin, elongate setae only ( Fig. 17B View Fig ). Surstylus ovoid with a patch of three setae apically ( Fig. 16B–C View Fig ) ............................................................................ S. altus sp. nov. (ECU)

46. Interfrontal bristles in three pairs, middle pair largest..................................................................... 47

– Interfrontal bristles in four pairs, first very small, other three subequal.......................................... 48

47. Mid tibia of both sexes with three dorsal setae in proximal half (two anterodorsal, one posterodorsal). Acrostichal setulae in 8–9 rows between anterior dorsocentral bristles. CS2 0.7–0.8 × CS3. Male S5 with a dark, inverted Y-shaped posteromedial sclerite flanked by a pair of converging, subtriangular, long-setose lobes ( Fig. 21B View Fig ). Lateral pieces of female T8 wide, subquadrate with setae well separated from ventral corner; female S8 reduced to a pair of minute lateral sclerites; spermathecae spherical with a shallow apical and a deep basal invagination ( Fig. 22D View Fig ) ............. S. azulensis sp. nov. (ECU)

– Male mid tibia with only a single anterodorsal seta at about midlength; female mid tibia with three dorsal setae in proximal half (two anterodorsal, one posterodorsal). Acrostichal setulae in 6–7 rows between anterior dorsocentral bristles. CS2 1.0 × CS3. Male S5 with a dark, elongate, posteromedial patch of dense setulae ( Fig. 85B View Fig ). Lateral pieces of female T8 narrow, distinctly rectangular with setae extending to ventral corners; Female S8 well developed with four small setae and dense medial setulae; spermathecae bean-shaped with a large but not deep subbasal invagination ( Fig. 86D View Fig ) ................................................................................ S. mandibulum sp. nov. (BOL, ECU)

48. CS2 0.9–1.0 × CS3........................................................................................................................... 49

– CS2 0.7–0.8 × CS3........................................................................................................................... 54

49. Wing hyaline. Male mid tibia with double ventral row of setae along apical two-thirds. Female hypoproct with a sclerotized anteromedial process covered in slightly thickened setulae ( Fig. 141B View Fig )......................................................................................... S. tridens sp. nov. (BOL, ECU)

– Wing at least slightly infuscate. Male mid tibia with double ventral row of setae along apical third at most. Female hypoproct membranous anteromedially, without a sclerotized anteromedial process ........................................................................................................................................... 50

50. Foreleg yellow. Male S5 with microtomentose posteromedial area ( Fig. 112B View Fig ). Surstylus tall, 0.9– 1.0 × height of epandrium ( Fig. 111C View Fig ).............. S. plumiseta ( Duda, 1925) (BOL, BRA, PER, PRY)

– Foreleg brown. Male S5 with a patch of dense setulae or long setae. Surstylus short, 0.4–0.5× height of epandrium.................................................................................................................................... 51

51. Male S5 gently curved along posterior margin with a posteromedial patch of long setae ( Figs 27B View Fig , 103B View Fig ); sclerite A bifurcate and setulose posteriorly (as in Fig. 27B View Fig ); sclerite E with stout setae or dense setulae posteriorly. Pseudocercus absent; subcercus large and broad, larger than surstylus. Postgonite broad, straight, and truncate apically ............................................................................. 52

– Male S5 produced posteriorly with a posteromedial patch of dense setulae ( Figs 70B View Fig , 79B View Fig ); sclerite A rounded and bare; sclerite E bare. Pseudocercus free from epandrium; subcercus small and tapered, smaller than surstylus. Postgonite narrow, sharply bent in apical third, flared and pale apically ... 53

52. Eye height 4.0 × genal height. Left lobe of sclerite A subequal to right lobe and apically pointed, with only setulae ( Fig. 27B View Fig ); sclerite E with a posterior patch of dense setulae. Basiphallus strongly bent in lateral view .................................................................... S. bucki sp. nov. (BOL, CRI, ECU, PER)

– Eye height 3.5× genal height. Left lobe of sclerite A larger than right lobe and apically rounded, with two setae in addition to setulae ( Fig. 103B View Fig ); sclerite E with a posterior patch of stout, thickened setae. Basiphallus gently curved in lateral view............................. S. paranebulosus sp. nov. (VEN)

53. Eye height 4.0× genal height. Medial patch of setulae on male S5 1.5× as long as wide ( Fig. 70B View Fig ). Surstylus subtriangular with apex elongate, curved anteriorly and blunt ( Fig. 69C View Fig ). Female S7 widely desclerotized along posterior margin with four large setae and 10–14 smaller setae ( Fig. 71B View Fig ); S8 split into two large lateral sclerites .................................. S. latibarbus sp. nov. (GTM, HND, MEX)

– Eye height 3.5× genal height. Medial patch of setulae on male S5 2.1× longer than wide ( Fig. 79B View Fig ). Surstylus hatchet-shaped, anterior edge straight, posterior edge broadly rounded ( Fig. 78C View Fig ). Female S7 sclerotized along posterior margin with four very large setae, 18–22 small setae, and a distinct posteromedial lobe bearing 3–4 large setae ( Fig. 80B View Fig ); S8 reduced to two minute lateral sclerites ........................................................................... S. longibarbus sp. nov. (CRI, GTM, MEX)

54. Male S5 with a dark, posteromedial patch of dense setulae (as in Fig. 123B View Fig )................................ 55

– Male S5 with short or long posteromedial setae, but not a patch of dense setulae ......................... 57

55. Surstylus subtriangular, tapered towards apex (131C). Subcercus large and pointed apically. Anal fissure short, semicircular ( Fig. 131B View Fig ). Postgonite dramatically expanded apically ( Fig. 132A View Fig ) ............................................................................................... S. rostrum sp. nov. ( MEX)

– Surstylus subquadrate or subrectangular, distinctly flat/truncate apically. Subcercus small and truncate apically. Anal fissure larger, subtriangular. Postgonite relatively slender throughout length.......... 56

56. Male S5 with posteromedial patch of dense setulae elongate, 2.0× as long as wide and flanked by bare, pale areas and dark, setose patches, anterior half of S5 with two large, pale areas on either side of midline ( Fig. 123B View Fig ). Surstylus stouter, 0.8 × as long as broad. Female S7 rectangular, posteromedially flat with sparse setae; S8 with a large, recurved ventral lobe ( Fig. 124B–C View Fig ); hypoproct elongate.................................................................................. S. recurvatus sp. nov. (CRI)

– Male S5 with posteromedial patch of dense setulae broader, 1.4× as long as wide and flanked by uniformly pigmented, setose patches, anterior half of S5 with two converging pale lines making a V-shape ( Fig. 134B View Fig ). Surstylus more elongate, 1.8 × as long as broad. Female S7 with a small posteromedial lobe and many long setae; S8 reduced to a pair of small lateral sclerites ( Fig. 135B View Fig ); hypoproct short ............................................................................... S. synorios sp. nov. ( MEX, USA)

57. Anterior (postsutural) dorsocentral bristle 0.7× length of posterior (prescutellar) bristle. Male S5 dark, produced and bare posteromedially; sclerite A forming a rectangular, entirely densely setulose area on the posterior margin of S6+7 ( Fig. 117B View Fig ). Subcercus wedge-shaped with a posteriorly elongate apex. Surstylus subtriangular, apical third tapered, anterior side with a triangular notch ........................................................................................................ S. puyensis sp. nov. (ECU)

– Anterior (postsutural) dorsocentral bristle 0.4× length of posterior (prescutellar) bristle. Male S5 desclerotized, simple and setose posteromedially; sclerite A projecting from S6+7 as two setulose lobes ( Fig. 94B View Fig ). Subcercus relatively parallel-sided and rectangular, apex rounded with a small, dorsal, preapical lobe. Surstylus stout, subquadrate............ S. nebulosus sp. nov. (CRI, ECU, VEN)