Aulacocheilus subrotundus ( Macleay, 1825 )

Tawde, Gaurang, Pawar, Meehir & Patwardhan, Amol, 2025, Clarifying species boundaries: Taxonomic revision of Aulacocheilus subrotundus (Macleay, 1825) (Coleoptera: Erotylidae) and its life cycle, Zootaxa 5725 (1), pp. 127-134 : 128-132

Aulacocheilus subrotundus ( Macleay, 1825) reinstated state

Engis subrotunda Macleay, 1825: 42 .

Aulacocheilus [sic] subrotundus (Macleay) – Gemminger and Harold 1876: 3702 (combination; “gen. dub.”)

Adult Diagnosis. Adults of A. subrotundus can be easily distinguished from other Indian Aulacocheilus species by the bands on the margins of elytra, as bands of A. subrotundus have distinct projections of the anterior and posterior margin making it irregular although symmetrical. A. subrotundus has a distinct dark spot on the elytral humeral region.

Adult description. Body sub-oval, moderately convex in lateral view, widest at the elytral base ( Fig. 1 ). General colour black; funicle of the antennae, palps, and tarsi yellowish-brown; elytron with 2 jagged yellow transverse bands, one at the apical third, and one occupying most of the basal margin leaving a black spot over the humerus. The coloration of the adult male ( Fig. 1 A-B) before preservation in alcohol is similar to that of the female ( Fig. 1 C- D), and alcohol may have caused color changes.

Head coarsely and strongly punctate with the clypeus extremely short and not emarginate. Maxillary palp with basal palpomere slender and terminal palpomere strongly transverse. Labial palps with three palpomeres; palpi very short and stout; the apical palpomere cupuliform and broader than long. Mandibles stout with bifid apex. Eyes large, prominent, and coarsely facetted.Antennae with 11 antennomeres ( Fig. 2), short, extending to the basal thirds of the pronotum, with short golden setae; antennomere III twice as long as antennomere IV; ratio of antennomeres I–XI lengths: 2.3, 0.8, 2.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.4, 1.1, 1.4; antennal club compact, with three antennomeres.

Thorax. Pronotum transverse, glabrous, and coarsely punctured; slightly less punctured than the head; posterior and lateral margins coarsely punctate with larger punctures. Lateral margins strongly elevated and nearly straight. Anterior angles bluntly rounded; posterior angles almost at right angled; posterior margin broadly lobed in the middle. Scutellar shield pentagonal.

Wings elongated ( Fig. 3A ), wide, and apically rounded with translucent membrane that frequently feature brown patches. Radial cell triangular. Elongate anal cell present. Ovate stridulatory area present on hind wings locks and rubs on elytron ridge. The subcosta, radius and media were highly sclerotized. Other veins and crossveins sclerotized and visible. Crossveins are present in Medial and Cubital regions. Vein MP3+4 and crossvein r3 are simple and unforked. Crossveins r3 and r4 are spaced and not contiguous. Elytral with 8 striae, intervals glabrous and smooth. Stridulatory area is present on the inner surface of the elytra ( Fig.3 B ).

Prosternum broad, pointed anteriorly, prosternal process emarginate posteriorly; semitriangular; sternal lines impressed around the coxal cavity; lateral prosternum with minute setae, and coarsely punctate, punctures large. Mesoventrite strongly transverse, glabrous, almost half the length of the prosternum; mesoventral lines continuous around the coxal cavity. Metaventrite long, with minute setae, strongly and coarsely punctate; more than three times as long as the mesoventrite.

Male genitalia ( Fig. 4A ) with penis stout and curved with an angled sclerotized projection at the base linked to the apophyses. Flagellum 2.6 times longer than the penis and apophyses 2.5 times longer than the penis. Penis surrounded by strongly sclerotized tegmen with fused arms. Parameres apically pointed and sclerotized with dense pubescent outgrowths.

Female genitalia ( Fig. 4 B-C) with coxites bearing narrow apical styli; both strongly sclerotized and pubescent. Spermatheca bean-shaped, slightly elongated, and sclerotized. Spermathecal duct distally sclerotized, duct half the length of spermatheca. Sclerotized Tergite VIII and median strut protruding from strongly sclerotized Sternite VIII.

Variation. Male (N =4): BL: 10.6 ± 0.08 mm; BW: 5.85 ± 0.06 mm; BR: 1.812 ± 0.008 mm. Female (N=6): BL: 12.08 ± 0.02 mm; BW: 6.28 ± 0.02 mm; BR: 1.923 ± 0.006 mm.

Material examined. Holotype of A. quadripustulatus ( Fabricius, 1801) ( Fig. 5 A-B) is labeled: “4pustulatus” [yellow paper, hand written]/ “ TYPE ” [red paper] ( ZMUK). The type of A. subrotundus ( Macleay, 1825) ( Fig. 5 C- D) is labeled: “Subrotunda. Mac.” [yellow paper, hand written]; “ Java (Horsfield.)” [yellow paper]; “188” [white paper, hand written]; “85” [white paper, hand written]; “ 60.5 E.I.C.” [white paper]; “Type” [white paper]; “ NHMUK 015997680” [white code label] ( NHML).

Recent specimens. A total of 10 recent adult specimens ( 4 males and 6 females), 40 eggs, 3 larval specimens and 1 pupa were examined with the following label data: “ Aulacocheilus subrotundus ( Macleay, 1825) . Mumbai, MH, India. 09 XI 2022. Coll.: Pranav Joshi. Det.: Gaurang Tawde & Meehir Pawar (2023)” [typed] ( ZKJSSC) .

Remarks. Fabricius (1801) described A. quadripustulatus (= Erotylus quadripustulatus or E. 4-pustulatus) based on a specimen collected from Sumatra. Macleay (1825) described A. subrotundus (= Engis subrotunda ) from Java, Sumatra. Lacordaire (1842) described eight species of Aulacocheilus and transferred E. quadripustulatus to the genus and placed E. subrotunda as a junior synonym. However, he cast some doubt in their synonymy. Bedel (1871) stated E. subrotunda was not the same species as A. quadripustulatus and that E. subrotunda possibly belonged in a different genus. Other subsequent authors ( Arrow 1909, 1925; Kuhnt 1911) considered A. subrotundus as a synonym of A. quadripustulatus . It seems likely that none of these authors studied the types of both species.

To resolve our questions on the identity of these species, photographs of the types were requested and received from ZMUK and NHML. Upon comparing the images, it is obvious that these were different species. Thus, A. subrotundus is here raised from synonymy and reinstated to full species status .

Another variety from India, Aulacocheilus quadripustulatus var. andamanus Achard (1923) , has been named, but varieties have no nomenclatural status. However, Archard describes the jagged edges of the elytral maculae, which is more similar to A. subrotundus . Hence, the presence of A. quadripustulatus in Andaman and India seems questionable. We consider our specimens from Mumbai and those discussed by Arrow (1909, 1925) to be A. subrotundus . A modern revision is needed to help understand the relationships between all species in Aulacocheilus .

Life History. The entire life cycle of A. subrotundus occurs from the late monsoon (September) to early winter season (December). The life stages seem to be completely dependent on the host fungi indicating obligatory relationship ( Fig. 6 ). The host fungus seems to be a member of the family Irpicaceae (Order Polyporales ). Dissection of a female revealed the presence of eggs. Larval stages emerge during the initial growth of fungal hymenium. They feed on all parts of the host fungus and pupate inside the fruitification. The adults emerge from the fruiting bodies of fungus and feed on fungal hymenium. In the absence of the host fungus, the adults were found under the bark of the tree. Mating pairs were seen on the fungus and under the tree bark.

Immature descriptions. Eggs. (n= 40); length: 1.85 ± 0.025 mm; width: 0.675 ± 0.037 mm ( Fig. 7A ). Elongate, oval, cylindrical, and yellowish white Larva. The 2 nd instar ( Fig. 7 C-E). (BL 4.2 mm), 3 rd instar (BL 10 mm) and 4 th (Final) instar (BL 15.5 mm) were examined. Oligopod larvae, body elongated, cylindrical, ventrally flat, and parallelsided, covered with stiff unbranched bristles. Head highly sclerotized, slightly flattened, and hypognathous, with short antenna with 3 antennomeres. Setiferous tubercles on abdomen and thorax. Legs well-developed, 5-segmented. Tergite IX bears a hook-shaped urogomphi in all instars. The size of urogomphi is proportionally smaller and more sclerotized in later instars as compared to initial instars. Pupae. BL 10.2 mm and BW 4 mm. Exarate pupa ( Fig. 7B ). Colour light to dark brownish yellow, oblong, ventrally glabrous but pubescent dorsum. Head sclerites similar to that of adults. Pronotum is slightly transverse, similar in shape to that of adults. Mesonotum and metanotum exposed dorsally and smaller in length and width than the pronotum. Elytral and wing thecae resting under median legs and partially covering the posterior legs. Abdomen with 9 segments, urogomphi present at segment IX.

Figures

FIGURE 1. Aulacocheilus subrotundus dorsal and ventral habitus. A. Male, dorsal. B. Male, ventral. C. Female, dorsal. D. Female, ventral.

FIGURE 3. Aulacocheilus subrotundus. A. Wing venation (scale = 2mm). B. Elytra inner surface (scale = 5mm).

FIGURE 4. Aulacocheilus subrotundus male and female terminalia.A. Male genitalia.B. Female genitalia. C. Female abdominal segment VIII.

FIGURE 5. Type specimens, habitus, and labels. A–B. Aulacocheilus quadripustulatus (Fabricius) holotype from ZMUK (Courtesy M. Kuhlmann). C–D. Aulacocheilus subrotundus (Macleay) type specimen from NHML (courtesy M. Barclay and M. Schlossman).

FIGURE 6. Live photographs A. Larvae of A. subrotundus. B.Adult of A. subrotundus. C. Host fungus (Polyporales: Irpicaceae) from which adults and larvae were collected. Location: Aarey Colony, Goregaon, Mumbai, Maharashtra, India.

FIGURE 7. Aulacocheilus subrotundus. A. Eggs. B. Pupa. C–E. Larval habitus. C. 2nd Instar. D. 3rd Instar. E. Final Instar