Guangzhou fungus beetle (Dichodontocis guangzhouensis) similar to Dichodontocis uncinatus and Dichodontocis queenslandicus

NEWS - Guangzhou fungus beetle (Dichodontocis guangzhouensis sp. nov.) and larvae from Guangdong Province, China, were described as a new species to science similar to Dichodontocis uncinatus Kawanabe (1994) and Dichodontocis queenslandicus (Lawrence, 2016).

Currently, only 3 species of Dichodontocis Kawanabe are known in the world. The type species, D. uncinatus is distributed in southwestern Japan (Yakushima Island). D. queenslandicus is found in the rainforests of Australia (Queensland). The new species is known from Guangzhou (Tianlu Lake Forest Park), China.

D. guangzhouensis is similar to D. uncinatus with the elytral setae appearing more distinctly seriate and regular in that species than in D. guangzhouensis, both anal veins of the hindwing are absent, but in D. guangzhouensis the hindwing has apical color spots and the impression of the anterior margin of the pronotum of D. guangzhouensis is broad and deep and extends posteriorly, clearly beyond the base of the horns, while in D. uncinatus the impression of the anterior margin of the pronotum is only between the bases of the horns and is much weaker than in D. guangzhouensis.

The terminalia are somewhat different. In D. uncinatus, the eighth abdominal sternite has a posterior margin that is slightly notched in the middle, and a strongly notched anterior margin. However, in the new species, the eighth abdominal sternite has a posterior margin that is broadly notched in the middle, the anterior margin is not notched in the middle.

The tegmen is broad at the base and gradually narrows near the tip in D. uncinatus. In the new species, the tegmen is wide at the base, from 1/5–4/5 of the base, the sides are almost parallel, and gradually narrows near the tip, slightly curved.

The new species is also similar to D. queenslandicus. The size and dimensions of the two species are similar. However, there are some differences between the two species. The head is relatively and mostly open, partially visible from above in D. queenslandicus. The head is almost completely open, visible from above in the new species.

The anterior margin impression of the pronotum of D. guangzhouensis appears to be wide and deep and extends posteriorly, clearly beyond the base of the horns, while in D. queenslandicus the anterior margin impression of the pronotum is slightly weaker and more anterior than in D. guangzhouensis.

The tegmen of D. queenslandicus is 4 times longer than wide, and the pen is 4 times longer than wide. The tegmen of the new species is 6.4 times longer than wide, and the pen is 8.0 times longer than wide. Sternit VIII of D. queenslandicus is posterior edge slightly emarginate in the middle, eighth abdominal sternite of the new species with posterior edge broadly emarginate in the middle, anterior edge not emarginate in the middle.

DESCRIPTION

Adult male. Fully pigmented adult. Measurements in mm: TL 1.511, PL 0.678, PW 0.695, EL 0.833, EW 0.717, GD 0.636. Ratios: PL/PW 0.98, EL/EW 1.16, EL/PL 1.23, GD/EW 0.89, TL/EW 2.11.

Body elongate, convex, reddish brown to dark brown; dorsal setae, tarsi, antennae (except club), maxillary palpus and labial palpus are pale yellow; dorsal vestiture dual, consisting of long and short erect setae.

Head wider slightly than long, partially visible from above, with sparse punctures and dual setae, frontoclypeal strongly elevated forming a pair of broad-based, reflexed at each side subtriangular plates, behind eyes. Compound eyes are finely facetted and suboval, each bearing approximately 70 ommatidia; GW 0.17 mm.

Antennae bearing 10 antennomeres with the following lengths (in mm): 0.07, 0.05, 0.04, 0.03, 0.02, 0.02, 0.02, 0.05, 0.05, 0.08. Mandibles are asymmetrical (misaligned), with well-developed, transversely ridged molae.

Pronotum is as long as broad and parallel-sided, which is slightly raised in the middle with shallow and fine punctures bearing short and long dual setae, erect. Punctures are separated by a distance equal to one to two diameters. Lateral margins are narrow, and not visible for their entire lengths from above.

Anterior edge produced forward and upturned into two small lateral projections. The anterior edge deeply and broadly emarginate in the middle just like a horseshoe, and the impression of the anterior margin of the pronotum extends posteriorly, distinctly beyond the bases of the horn. Anterior angles obtuse. Posterior margin feebly bisinuous posterior angles rounded.

Scutellar shield developed, with a few punctures and setae; subtriangular, BW 0.13 mm. Elytra 1.2 times as long as broad, 1.3 times as long as pronotum; punctures rough; setae dual short and long, inclined and suberect; sides subparallel in basal 2/3, then gradually convergent apical.

Hind wings are fully developed, nearly pellucid. The venation type is folding patterns. Strongly reduced venation patterns of the clavus, anal vein absent. A medial field with one vein and a small fleck, a medial embayment, a small support sclerite near the wing apex; with a distinct cubitoanal strut and radiomedial loop. The hind wings are 3.3 times as long as broad, the widest part is in the middle, shrinking to the sides.

Protibia expanded to the apex, outer apical angle with 2 acute teeth and dentate along the outer edge which are shorter near the base and gradually becoming longer towards the apex. Meso-and metatibia expanded forming a rounded lobe lined with socketed spines.

Prosternum is weakly biconcave and subcarinate; the prosternal process is flaked and slender somewhat slightly broadened near the apex, slightly higher than the procoxae (best seen in lateral view).

Metaventrite is convex but slightly emarginate in the middle, with sparse punctuation and bristles; discrimen nearly one-fourth length of ventrite. Abdominal ventrites with fine setae and shallow puncture, the surface between them microreticulate; the first abdominal ventrite is 2.2 times as long as 2nd, the ventrites bearing a small, circular, not obvious and marginally pubescent fovea. The length of the ventrites (in mm) is as follows: 0.202, 0.093, 0.077, 0.072, 0.078.

Aedeagus 4.9 times as long as ventrite 5. Tegmen is slender 6.4 times as long as the widest, widest at the base and gradually narrower near the apex with the basal end subacute like a hook; narrowed gradually from base to apex; apex slightly bent.

Penis is shorter and narrower than the tegmen, 8.0 times as long as the widest, with a subacute apex and moderately long, sides parallel from basal to four fifth, then just like the rhombus near the end. The basal piece is weakly sclerotized, much longer than a broad, like a narrow horseshoe.

The sternite VIII with the posterior margin broadly emarginate in the middle, with several short hairs on each side, anterior margin not emarginate. The tergite VIII with the posterior margin not emarginate in the middle, anterior margin strongly emarginate.

Measurements (n = 3, including the holotype; mm): TL 1.48–1.51 (1.50 ± 0.02); PL 0.66–0.68 (0.67 ± 0.01); PW 0.70–0.71 (0.70 ± 0.01); EL 0.83–0.84 (0.87 ± 0.01); EW 0.70–0.72 (0.71 ± 0.01); GD 0.63–0.64 (0.64 ± 0.01).

Female. Similar to male, except for the following points: frontoclypeal without strongly subtriangular plates; pronotum with anterior edge broadly rounded, without projections; first abdominal ventrites without a sex patch. The eighth abdominal sternite of females is different from males.

The posterior margin is not emarginate in the middle which is flat and the anterior margin is strongly emarginate in the female. Female genitalia is as long as wide, widest at the middle; paraprocts is 0.85 times as long as gonocoxites.

Measurements (n = 6; mm): TL 1.18–1.48 (1.33 ± 0.10); PL 0.46–0.60 (0.55 ± 0.06); PW 0.51–0.65 (0.59 ± 0.06); EL 0.72–0.90 (0.78 ± 0.07); EW 0.58–0.70 (0.65 ± 0.44); GD 0.56–0.74 (0.67 ± 0.08).

Later instar larva; 1.69 mm long, 0.35 mm broad, head-capsule of 0.31 mm wide. The body is opal and translucent except for the head, pretarsus (claw) and pygidium, which are light yellow to dark brown.

Body elongate, more or less parallel-sided, subcylindrical, slightly curved ventrally. Surfaces are relatively smooth except for the mouth frame and tips of urogomphi, rarely with light tergal plates on most segments, smooth with vestiture of scattered long and short setae.

Head subspherical, protracted and moderately to strongly declined (hypognathous); posterior edge not emarginate. The epicranial stem is long with median endocarina beneath it; frontal arms are Y-shaped, with five stemmata on each side.

Antennal insertion is a well-developed and concealed maxillary articulatory membrane. Antennae are very short with 2 segments which have a sensorium on the first segment and a long seta on the apical antennomere. The 1st segment is wider and shorter than the 2nd.

Mandibles are large, robust, asymmetrical, and bidentate (one is large and the other is small), with a simple and transversely cutting edge. Ventral mouthparts retracted; stipes longer than wide; maxillary articulating area reduced; galea rounded; lacinia represented by a short, truncate, subapical, lobe on the dorsal surface (ventral side not visible); palp 3-segmented.

Labium with submentum, mentum, bearing short ligula and 2-segmented palps. Hypopharyngeal sclerome absent. Hypostomal rods absent; ventral epicranial ridges present. Gula is wider than long, fused to the submentum. Thoracic terga without transverse carinae or rows of asperities. Prothorax is only slightly larger than meso- or metathorax.

Prosternum without special armature. Thoracic legs are short and broad, subequal; 5-segmented with pretarsus (claw), bearing a few setae; coxae relatively close together. The length of the abdomen is more than twice as long as thorax; terga and sterna without patches.

Terga IX is slightly transverse and longer and has variously modified, with concave and heavily sclerotized disc and with a pair of upturned urogomphi whose color is deepened from brown to black. There are 4–6 dark-colored, small protrusions between the urogomphi.

There are also five protrusions on each side of the terga. Segment X is transverse, posteroventrally oriented. It is only about ½ as long as terga IX; anal opening transverse. Spiracles are annular.

Measurements. Later instar larva (n = 5, mm): TL 1.33–1.75 (1.61 ± 0.17); Wide 0.31–0.35 (0.34 ± 0.02).

Original research

Li N, Xu J-S (2024). The first record of the genus Dichodontocis Kawanabe, 1994 (Coleoptera, Ciidae) from China, with the description of a new species and its larva. ZooKeys 1218: 167-176, DOI:10.3897/zookeys.1218.130088

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