Micropathus Richards, 1964

Genus Micropathus Richards, 1964 View in CoL

Micropathus Richards, 1964: 217–218 View in CoL .

Type species

Micropathus tasmaniensis Richards, 1964 View in CoL .

Etymology

An apparent reference to Macropathus Walker, 1869 , the namesake of ‘Macropathinae’, but not explained by either Walker or Richards. Potential origins for the suffix ‘-pathus’ include the Ancient Greek ‘páthos’ (strong feeling) or the Romance ‘pata’ (); these terms may have been in reference to the elongated legs or antennae characteristic of Rhaphidophoridae for sensing in the dark. However, as Micropathus and Macropathus have similar morphology in this regard, it is unclear which structure(s) Richards was alluding to when naming the genus. The grammatical gender of the genus is masculine.

Description

Micropathus comprises medium-sized crickets with a body length of up to 20 mm. Individuals range from mid to dark brown and the thoracic nota are generally mid brown and mottled with ochreous brown patterning (e.g.,). The fore coxae bear a single anterolateral spine; all other coxae are unarmed. The fore and middle femora consistently bear one apical spine each on the prolateral and retrolateral surface, whereas in the hind femora this character is absent prolaterally and variably present retrolaterally. The tibiae have two pairs of apical spines, one each on the superior and inferior surfaces; on the hind tibiae, there are two additional pairs of small, subapical spines situated within each primary apical pair (subapical spines).

Linear spines of the fore and middle legs are present as an average of four pairs on the ventral surface of the tibiae, with one member of each pair facing prolaterally and the other retrolaterally. The number of dorsal linear spines on the hind legs varies by species and life stage. However, in most species the ventral surface of the hind femora is unarmed prolaterally, and linear spines are variably present (0–5) retrolaterally. The genus can be split into two broad groups on this basis: species with ventral linear spines variably present on the retrolateral surface of the hind femora ( M. montanus , M. cavernicolus , M. zubat Beasley-Hall sp. nov., and M. fuscus ) vs species always lacking those the surface is completely unarmed; ( M. tasmaniensis , M. kiernani , and M. ditto Beasley-Hall sp. nov.). These differences are reflected in the genus being split into two major phylogenetic clades as in Fig. 1a View Fig . The hind tibiae generally bear 25– linear spines on either side of the dorsal surface, and the first and second tarsal segments between 0–4 on either side of the dorsal surface.

Parvotettix Richards, 1968 and Tasmanoplectron Richards, 1971 are the two other genera described from Tasmania proper (i.e., excluding the islands of the Bass Strait) and Micropathus can be differentiated from them relatively easily based on leg spination. In Parvotettix , the fore and middle legs are almost without spines: apical spines are restricted to the tibiae only (vs the tibiae and femora in Micropathus ) and linear spines only occur on the dorsal surface of the hind tibia, where they are few but extremely long and visible from a distance with the naked eye. Individuals of Parvotettix tend to rest on substrate with their legs folded close to the body rather than splayed wide as in Micropathus ( Richards 1970) . Parvotettix is also much smaller and more strongly pigmented compared to Micropathus , with most species appearing dark brown to black ( Richards 1968, 1987). Similarly, Tasmanoplectron bears linear spines on both the dorsal as well as ventral surfaces of the middle tibia; this character only occurs on the ventral surface in all other Australian Rhaphidophoridae , including Micropathus ( Richards 1971a) . Tasmanoplectron also has teeth on both the ventral and lateral surfaces of the ovipositor, whereas in all other genera these are restricted to the ventral valves only.

Finally, Micropathus has several synapomorphies helpful in distinguishing it from all other Australian Rhaphidophoridae . Firstly, the distal margin of the male suranal plate is curved ventrally and is sclerotised and dark on the underside, with this thickening of the cuticle often produced into a row of tubercles or spines. While similar curvature also occurs in Tasmanian and New Zealand Macropathinae , such projections are unique to Micropathus . Secondly, the female subgenital plate is split medially at the distal margin into two distinctive, spiked lobes ( Fig. 2 View Fig ), which in adults may be sclerotised at the apex or in their entirety (see Remarks). Most other Australian genera also bear these lobes, but they occur in a trilobed configuration when present and the structures are generally wide, sloping, and less clearly demarcated from the subgenital plate.

Remarks

Richards confused ‘ prolateral ’ and ‘ retrolateral ’ in her original descriptions of Micropathus , necessitating the redescriptions presented here. She used these terms to refer to the positioning of spines facing the anterior (prolateral) or posterior (retrolateral) ends of the body, leading to the incorrect reporting of spine counts helpful for distinguishing species. Richards also apparently overlooked intraspecific variation in several characters related to the legs and terminalia. note that Richards referred to the distinctive lobes projecting from the distal margin of the female subgenital plate as sclerotised ( Fig. 1 View Fig ). While we agree that the structures do appear to be markedly sclerotised in some specimens – e.g., M. montanus and M. zubat Beasley-Hall sp. nov. – we consider it possible that for species with more delicate lobes, the structures are darkened because of tissue damage. In Rhaphidophoridae , the ventral female subgenital plate makes contact with the dorsal male suranal plate during copulation and the structures are thought to stabilise mating pairs ( Stritih & Čokl 2012). We have exmined several species of Micropathus with lobes with darkened, delicate, and jagged apices only seen in adults, whereas the structures are rounded and uniform in younger females. Thus, we consider this could result from breakage in life and may not reflect interspecific variation.

Key to the species of Micropathus Richards, 1964 View in CoL

1. Ventral surface of hind femur with linear spines. Male subgenital plate rounded, often not readily distinguishable from preceding sternite 9 (e.g., Fig. 9c View Fig ) .................................................................. 2

– Ventral surface of hind femur without linear spines. Male subgenital plate bulbous, pronounced from preceding sternite 9 (e.g., Figs 6c View Fig , 8c View Fig ) .............................................................................................. 5

2. Body colouration predominantly dark brown with mid brown patterning ( Fig. 7 View Fig ). Hind femur with ventral linear spines prolaterally. Female subgenital plate concave distolaterally, bearing two long, distomedial lobes ( Fig. 2d View Fig ). Male suranal plate with straight proximal margin, notched distally ( Fig. 2d View Fig ) ..................................................................................................... M. fuscus Richards, 1968 View in CoL

– Body colouration mid brown (e.g., Fig. 5 View Fig ). Hind femur with ventral linear spines retrolaterally only ................................................................................................................................................... 3

3. Female subgenital plate strongly concave laterally and with horn-like projections at distolateral corners ( Fig. 2a View Fig ). Proximal margin of male suranal plate forming three rounded lobes margin rounded ................................................................................................ M. montanus Richards, 1971 View in CoL

– Female subgenital plate straight to convex laterally, convex distolaterally ( Fig. 2b–c View Fig ) ................... 4

4. Distolateral portion of female subgenital plate with broadly square, sclerotised corners; two sclerotised lobes at distal margin separated by wide medial notch ( Figs 2c View Fig , 9e View Fig ). Proximal margin of male suranal plate forming three rounded lobes; distal margin with faint medial notch ( Fig. 2c View Fig , 9b View Fig ) ............................................................................................................ M. zubat Beasley-Hall sp. nov.

– Distolateral portion of female subgenital plate rounded; two lobes originating from medial surface of plate and separated by a furrow; distal margin of plate with a deep but narrow medial notch ( Figs 2b View Fig , 4b View Fig ). Male suranal plate oval-shaped and rounded at proximal and distal margins ( Fig. 2b View Fig ) ........ .......................................................................................................... M. cavernicolus Richards, 1964

5. Lobes originating from medial surface of female subgenital plate, measuring at least half length of plate ( Figs 2g View Fig , 6e View Fig ). Male suranal plate with rounded proximal margin and a moderate medial notch on distal margin ( Figs 2d View Fig , 6b View Fig ). Male subgenital plate pale and with a prominent triangular apex ( Fig. 6c View Fig ) ............................................................................................................................................... ............................................................................................................. M. ditto Beasley-Hall sp. nov.

– Lobes originating from distal margin of female subgenital plate, measuring less than half length of plate ................................................................................................................................................... 6

6. Body colouration mid brown. Lobes on female subgenital plate measuring around a quarter length of plate and separated at their bases by a medial furrow ( Figs 2e View Fig , 8e View Fig ). Distal margin of male suranal plate uninterrupted or with a faint medial notch (Fig.). Male subgenital plate uniform in colour to preceding sternite and with a rounded, poorly pronounced apex ( Fig. 8c View Fig ) ........................................ ........................................................................................................ M. tasmaniensis Richards, 1964 View in CoL

_ Body colouration uniformly dark brown. Distal margin of male suranal plate uninterrupted ( Fig. 2f View Fig ). Lobes on female subgenital plate short, measuring around an eighth length of plate, and touching at their bases ( Fig. 2f View Fig ). Female subgenital plate rounded laterally and distally ..................................... ................................................................................................................. M. kiernani Richards, 1974