Bagous (Macropelmus) obrieni Mahendiran, 2025

Bagous (Macropelmus) obrieni Mahendiran sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:D3DD0289-6EE5-44C7-B28B-5AA6B4215AD2

( Fig. 1 View FIGURE 1 & 2 View FIGURE 2 )

Material Examined: Holotype: Male, India, Karnataka, Nayakanapalya Lake at Savandurga betta view point (12°54ʹ24.5ʺN 77°16ʹ40.6ʺE), Nymphoides indica , 14. ii. 2024, leg. Manu B. GoogleMaps ; Paratypes: 2 males and 12 females, same data as the holotype GoogleMaps ; 1 male and 5 females, same data as the holotype except “leg. Mahendiran G.” GoogleMaps (all in (ICAR-NBAIR).

Description: Holotype male:Body medium sized(4.86mm), elongate oval,moderately slender( Fig. 1 View FIGURE 1 ). Rostrum long, 1.35× as long as prothorax; dark brown up to antennal insertion, apically reddish brown; almost flattened, parallel sided, slightly broadened after antennal insertion; dorsal and ventral curvature nearly straight in lateral view ( Fig. 2a View FIGURE 2 ); median basal carina lacking; basolateral carina lacking; apicolateral carina lacking; apical median carina lacking; basolateral sulcus shallow, narrow, short, shallowly punctate; ventral margin not angulate, not carinate; scrobe visible from above only at point of insertion, basally with ventral margin straight or almost so, with ventral margin meeting rostral margin at very acute angle, reaching middle of eye ( Fig. 2b View FIGURE 2 ); scales sparse basally; punctures deep at base, moderately deep up to antennal insertion, sparse, shallow and finer apically. Head black, weakly convex, impressed; eyes moderately convex; with small, deep punctures; with plumose scales yellowish, on articulating area; Supraocular setae few, very short, distinct, suberect, curved at apex, slender. Frons black, glabrous, rugose with deep punctures, without submedian setae; broad, 0.74× as wide as head across eyes, flattened, impressed, not set off from rostrum by impression; Antennae inserted almost middle and laterally; scape long, slender, subclavate; scape and funicle golden brown; funicle 7-segmented, moderately short, 0.44× as long as scape, segment 1 stout, segment 2 slender, 1 and 2 subequal in length, 3-5 short and transverse, first, sixth and seventh funicular segments with row of whitish subrecumbent setae; seventh funicular segment not distinctly separated from the club; club broad-oval, uniformly pubescent, reddish brown; Prothorax transverse, black except reddish brown apex, glabrous, flattened, rugose with moderately deep punctures with uneven undulations, 0.88× as long as broad; sides subparallel from base to 3/4 th of pronotum, very weakly expanding from base, slightly bisinuate basally, truncate apically ( Fig. 2c View FIGURE 2 ); with apical constriction strong in apical l/4, without longitudinal carinae, dorsally distinct and uniform, laterally weakly rounded behind constriction, with sides slightly impressed behind round area, lacking pit near margin of prosternal sulcus; median sulcus lacking; apical setae few, scarcely evident, very short, subrecumbent, curved; marginal setae lacking; carina on basal margin lacking; scales granulate, pitted, contiguous, round, brownish; not maculate on disc; postocular lobes well-developed, deeply excavated below, with short, thick vibrissae below the eyes, whitish brown ( Fig. 2b View FIGURE 2 ). Prosternal sulcus deep, broad, weakly narrowed at apical constriction, biangulate; side margins moderately raised, lateral margin subacute just in front of coxae (lateral view), neither distinctly projecting over forecoxae nor bent inward ( Fig. 2d View FIGURE 2 ). Scutellum visible, black, round and rugosely punctate. Elytra subparallel behind humeri to declivity, 1.67× wider than prothorax; apices subacuminate, conjointly moderately emarginated; humeri well-developed, weakly obliquely angulate, slightly projecting ( Fig. 2e View FIGURE 2 ); basal margin more or less flat, slightly swollen adjacent to scutellum; odd intervals not more convex nor elevated, interval 3 more or less uniformly elevated; odd numbered intervals flattened, broader than even numbered intervals which were also flat; base of interval 2, 3 and 6 impressed; disc weakly transversely angulately impressed across basal l/3, disc not undulating; antedeclivital swelling of 3 rd interval lacking; declivital callus of 5 th interval moderately well developed, subquadrate; confluence of intervals 3 and 9 slightly swollen; interval 2 and 3 slightly impressed near middle from base; strial grooves distinct, moderately deep, narrow; punctures minute, scarcely evident, elongate, narrow, deep, not wider than strial grooves; scales granulate, contiguous, pitted, round, greyish white; cuticle black. Abdominal sterna with small, irregular, moderately deep punctures; Sternum 1 with transverse impression at anterior margin, shallow, narrow; apical margin slightly declivous; 1.19× as long as 2; suture between 1 and 2 almost truncate, finely incised medially, deep laterally. Sternum 2 flattened, with transverse row of scarcely evident (often denuded) subrecumbent coarse setae, apical margin moderately declivous, not impressed on declivity, 1.48× as long as 3 & 4 together. Sternum 5 with pair of sub-basal lateral impressions; with apicomedian area flat; basally flat; without tubercles; lateral impressions very shallow, large; with pair of apicolateral setae, 1.16× as long as 3 & 4 together, 0.77× as long as 2, 0.64× as long as 1. Legs moderately long; femora clavate, reddish brown. Trochanter having single long sub-erect setae. Tibiae moderately slender, reddish brown, inner margin almost straight, with outer margin moderately arcuate toward apex (in lateral view); apices not narrowed; with inner surface with denticles few, indistinct, minute, with few inconspicuous bristles on inner surface, bristles on outer surface lacking; with uncus long, moderately slender, longer than width of tibia1 apex; hind tibiae slightly arcuate as fore and midtibiae, inner surface possessing few very small denticles with short setae ( Fig. 2f View FIGURE 2 ). Tarsi long, linear, reddish brown, tarsomeres 1-3 slightly widened towards apex; tarsomere 1 0.76× as long as 2 & 3; tarsomere 2 and 3 subequal, subcordate; tarsomeres ventrally with dense, subrecumbent to recumbent pubescence, dorsally finely pubescent; claws golden yellow, widely separated ( Fig. 2k View FIGURE 2 ).

Male genitalia: Penis with dorsal surface, excluding orifice and area behind dorsal process, fully sclerotized ( Fig. 2g View FIGURE 2 ); with ventral surface fully sclerotized; widest at dorsal process, distinctly constricted behind dorsal process; elongate, more or less triangular, with extreme apex subtruncate, very bluntly rounded, moderately slender in lateral view, tapering and narrowly rounded ( Fig. 2h View FIGURE 2 ); post-orificial dorsal process directed slightly basad, setal brush lacking; dorsal surface behind dorsal process with broad, deep depression; with dorsal surface behind dorsal process membranous in broad oval area; dorsobasal margin distinct, shallowly emarginate; ventrobasal margin distinct, deeply emarginate. Orifice triangular, elongate; with proximal margin concealed by dorsal process ( Fig. 2i View FIGURE 2 ). Apodemes moderately robust, short, curving inward, 0.20× as long as penis. Tergum rhomboidal shape, basal apodeme 0.19× as long as median lobe, parameroidal lobes well-developed ( Fig. 2l View FIGURE 2 ). Spiculum gastrale slender, uniformly thick ( Fig. 2j View FIGURE 2 ). Internal sac Orificial sclerites lacking.

Female genitalia: Spiculum ventrale with apical setae lacking; arms slender, parallel, basally fused, inner margins more or less straight, convergent towards apex, outer margins broad, without emarginate; fenestral area open, elongated, kite shape ( Fig. 2n View FIGURE 2 ). Apodemes slightly divergent at extreme apex only, continuous to base with slightly widened base. Spermatheca ramus prominent, markedly extending past insertion of spermathecal duct, set off from body by markedly emargination; cornu blunt, rounded tip; nodulus irregularly wrinkled ( Fig. 2m View FIGURE 2 ).

Variability: Body range: length: 3.08-3.71 mm (without rostrum); width: 1.41–1.75 mm; rostrum 1.34–1.37× as long as prothorax; elytra 1.58-1.67× wider than prothorax; first sternum 1.18-1.25× as long as second; second sternum 1.47-1.52× as long as third & fourth together.

Comparative notes: Among all the species of the Bagous transversus group from India and other countries (see Remarks), this new species morphologically appears more similar to B. loisae ( Fig. 3a & b View FIGURE 3 ), from which it differs by both males and females having a longer rostrum, 1.34× as long as prothorax (vs 0.82× in B. loisae ); antennae inserted almost at middle of the rostrum, seventh funicular segment not distinctly separated from club; pronotum without marginal setae; elytra without any vittae and interval not elevated; abdominal sterna punctate (granulate in B. loisae ); tibial uncus long, moderately slender, longer than width of the tibial apex; median lobe without setal brush and denticles on dorsal process; spermatheca with distinct ramus ( Fig. 2 View FIGURE 2 ).

Etymology: This new species is named in honor of the late Dr. Charles W. O’Brien, an eminent American entomologist and world-renowned weevil taxonomist. He contributed immensely to the taxonomy of weevils, particularly the aquatic weevils of the world.

Collection Habitat: Specimens were collected from the leaves and flowers of Nymphoides indica , on which they fed on by making holes in the leaves ( Fig. 4a View FIGURE 4 ). They were also observed feeding on the pollen of Nymphoides indica ( Fig. 4b View FIGURE 4 ). The other aquatic plants present in the lake were mainly lotus and Hydrilla sp. , but no damage to these plants could be detected.

Distribution: The Republic of India consists of eight union territories and 28 states. The distribution of the genus Bagous shows that it is well distributed throughout India ( Table 1 View TABLE 1 ), covering two union (Delhi and Jammu and Kashmir) territories and 14 states (Andhra Pradesh, Assam, Bihar, Delhi, Haryana, Jammu and Kashmir, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh, West Bengal), other states and union territories can be explored for this important genus, as it is a potential biocontrol agent for the notorious aquatic weeds in ponds, lakes and other water bodies. This new species, Bagous (Macropelmus) obrieni , was collected from the lake at Savandurga Betta viewpoint, Nayakanapalya, Karnataka.

Remarks: The host plant of B. obrieni , Nymphoides indica (Water Snowflake) , is an aquatic weed of the family Menyanthaceae , which is a perennial, rhizomatous, free-floating plant. The native range of this species is probably tropical and subtropical Asia to Southwestern Pacific, but it is now widely distributed in temperate Asia, southern Africa, southern America, and more recently also in North America (Florida, Texas and North Carolina), where it is becoming invasive ( Saunders, 2005). No species of Bagous except two other Indian species, B. confusus O’Brien, 1995 and B. pyrrhocnemus Gyllenhal, 1836 ( Table 1 View TABLE 1 ), are reported to feed on Nymphoides indica ; however, it must be considered that the host plants are currently unknown for many species of Bagous . Therefore, with the possibility that our new species could be a possible introduction from another country or vice versa, we examined all other taxa of the B. transversus group, to which B. obrieni belongs.

According to Caldara et al. (2017), the B. transversus group, apart from the two already cited Indian species, B. loisae and B. similis , was previously composed by other six species: four from North America, B. cavifrons LeConte, 1876 , B. maculatus Blatchley, 1916 , B. texanus Tanner, 1943 , B. transversus LeConte, 1876 , and two Palaearctic, B. limosus (Gyllenhal, 1827) and B. youngi O’Brien & Morimoto, 1994 . Thanks to the opportunity to study specimens of all of them identified by Charles O’Brien, we ascertained that all are clearly different from B. obrieni .

In case of rapid expansion of Nymphoides indica , especially in southern USA as suspected ( Saunders, 2005), Bagous obrieni should be investigated for its biocontrol potential against this weed.