Terrobittacus Tan and Hua, 2009

Tan, Jiangli & Hua, Baozhen, 2009, Terrobittacus, a new genus of the Chinese Bittacidae (Mecoptera) with descriptions of two new species, Journal of Natural History 43 (47 - 48), pp. 2937-2954 : 2938-2941

Terrobittacus Tan and Hua , gen. nov.

Type species: Bittacus implicatus Huang and Hua in Cai et al. (2006).

Diagnosis

The new genus is related to Bittacus Latreille , but can be recognized by the following characters: (1) pterostigmal cross-vein (Pcv) only one (cf. generally two); (2) the fourth tarsomere of legs with only one spine on each side (cf. with three spines); (3) male epandrial appendage distinctly shorter than half length of gonocoxites (cf. longer than half length of gonocoxites); aedeagal lobe small and acute (cf. relatively large, various); sex pheromone gland single-lobed (cf. bilobed); dorsal portion of tergum X absent or strongly vestigial into a narrow transverse plate (cf. developed, saddle-shaped); (4) the two halves of the subgenitale almost fused completely in female (cf. separated to apex by a distinct suture of membrane); (5) egg spherical, decorated with distinct grid of latitudes, resembling a terrestrial globe (cf. spherical or cuboidal to polyhedral, not decorated like a terrestrial globe); (6) larval setae arising at the apex of dorsal protuberances conspicuously acerate, blackish brown (cf. clavate, pale grey).

The new genus also resembles Hylobittacus Byers , but differs by the following characters: (1) wing without pigmented apical spot (cf. with a conspicuous pigmented apical spot); (2) egg like a terrestrial globe (cf. decorated with fine reticulation); (3) larval setae arising at the apex of dorsal protuberances in all instars, conspicuously acerate, blackish brown [cf. arising at the subapex of the dorsal protuberances (except the first instar), clavate, pale grey]; (4) wings held on back roof-like when at rest (cf: wings kept separate).

Etymology

The genus name is derived from terra (the Latin name for the planet Earth) and Bittacus (a related hangingfly genus), referring to its relation to Bittacus and the resemblance of its egg to the terrestrial globe both in shape and in bearing distinct grids of latitude.

Description

Head yellowish brown; maxillary palp with the fifth segment about equal to the fourth; compound eyes black, wide apart below the antennae; three ocelli about similar in size; ocellar triangle black; antennae filiform; flagellum ciliated.

Thorax. Nota unevenly yellowish brown to black. Pleura pale yellow. Legs yellowish brown, with distal ends of femora and tibiae blackish brown; short black setae sparsely borne on femora, tibiae and tarsi; hind femora distinctly thicker than fore and middle femora; basal joint of hind tarsus little longer than second and third together; tarsomere IV with only one spine on each side.

Wings. Forewing hyaline with a faint yellowish tinge; pterostigma conspicuous with only one pterostigmal cross-vein (Pcv); two pale brown nygmata each present on cells R 4+5 and 1 R 5; a whitish thyridium at first fork of media ( FM) and at the base of M 4; three dark brown diffused flecks each at origin of radial sector (ORs), first fork of radial sector (FRs) and origin of media ( OM). Sc ending far beyond the level of FRs; subcostal cross-vein (Scv) near the ending point of Sc, beyond FRs; anal cross-vein generally absent; vein 1A terminating far before the level of FM; apical cross-veins arranged generally in two lines, along sectorial cross-vein 1s, 2s respectively; the number of cross-veins in the third line along 3s varying from zero to four in different species or individuals. Hindwing similar to the forewing, but 1A coalesces with CuP only for a short distance; Sc ending beyond the level of ORs, far before FRs; Scv approaching middle point of ORs and FRs.

Abdomen of male. Abdominal sex pheromone glands present at the membranous area between terga VI –VII and VII–VIII, single-lobed rounded; epandrial appendages (tergum IX) shorter than half length of gonocoxites, with a patch of apical spines on inner side; dorsal portion of tergum X either absent or vestigial into a narrow transverse plate; aedeagal lobes small and acute.

Abdomen of female. Subgenitale relatively small, two halves of subgenitale almost fused completely, with no conspicuous membrane area in ventral aspect. Tergum X narrow, extending slightly ventrad; supraanale and subanale short, truncate apically. Spermatheca subspherical, with a short rostrum.

Egg. Dark brown, spherical in shape. Tough and thick chorion is decorated with six grids of latitudes (outer two not distinct), looking like a terrestrial globe.

Larva. The larva undergoes four instars, eruciform and peripneustic. The head is hypognathous with a pair of compound eyes and a median frontal ocellus; somites are peculiar with rows of thick protuberances mostly branched medially, each bearing a setose seta apically; the setae arising at the apex of each dorsal protuberance in all instars are conspicuously acerate, blackish brown; anal segment terminates in a protrusile sucker.

Distribution

The Oriental region (southern China).

Remarks

The genus Hylobittacus Byers is hard to recognize based solely on dried specimens of adults for its generic characters, which overlap with those of Bittacus , especially the wing venations. A conspicuous pigmented apical wing spot might be the most useful. It seems that the six Eocene species of Hylobittacus recognized by Krzeminski (2007) from Baltic amber only by wing venations is not very convincing. A thorough and profound revision of the genus Bittacus worldwide is desperately needed.

Bittacus eremus Lambkin, 1988 , is the only representative of Bittacus from Australia. It is very similar to Terrobittacus in the following characters: (1) tergum X of male vestigial into a simple transverse dorsal plate; (2) sex pheromone gland single-lobed; (3) hind basitarsus slightly longer than the second and third tarsomere together; (4) gonostylus short and small; (5) supraanale and subanale of female short, truncate apically. However, it differs in: (1) epandrial appendage slightly longer than gonocoxites; (2) Pcv two in number; (3) aedeagal lobe without apical process and terminal filamentous extension; (4) length of the fifth segment of maxillary palp shorter than the fourth; (5) base of tarsomere IV with five spines on each side. Given that its immature stages are still unknown, and the Australian species is relatively special in distribution generally, it is too early to discuss its relation to Terrobittacus . What we can say is that its assignment to Bittacus is most probably questionable. Just as Lambkin (1988) mentioned, its taxonomic history as well as its very wide distribution suggest that Bittacus may be paraphyletic. Whiting (2002) also reached the same conclusion that Bittacus is paraphyletic based on molecular data.

Recently when the second Oriental hangingfly genus Bicaubittacus was established, a key to genera of Bittacidae was compiled and the major differentiating features among the 17 genera except Terrobittacus gen. nov. are summarized in the key ( Tan and Hua 2009). For this reason, we only present here a key to the four species of Terrobittacus as follows.

Key to species of the genus Terrobittacus (male)

1. Wing with the fork of M 1+2 (FM 1+2) slightly before the level of FR 4+5; crossveins r-m and m intercrossing M 1+2 at FM 1+2. Cerci longer than epandrial appendages. Gonocoxites bearing one to three pairs of long convergent apical bristles. Epandrial appendage with no ventral denticulate process, but bearing a cluster of more than 10 large black spines on its inner surface at the distal end.................................... T. longisetus sp. nov. Wing with FM 1+2 far beyond the level of FR 4+5; cross-vein r-m and m intercrossing M 1+2 before FM 1+2. Cerci distinctly shorter than epandrial appendages. Epandrial appendage produced ventrally into a denticulate process, its inner surface bearing numerous small black spines apically. Gonocoxites without long apical bristles...................................... 2

2. Blackish brown cloudings diffused along most cross-veins forming two noticeable bands. Proctiger pointed, with its apex rounded........................................................ T. echinatus comb. nov. No noticeable marked bands along cross-veins. Apex of proctiger not rounded..................................................... 3

3. Proctiger relatively thick; apex curved caudoventrally into a hook, like rostrum of a parrot............................ T. implicatus comb. nov. Proctiger slender, sabre-shaped, curved caudad, acute apically......................................................... T. xiphicus sp. nov.