Two new species of the genus Terrobittacus Tan & Hua , 2009 ( Mecoptera : Bittacidae ) from southwestern China with a key to species

Two new species of hangingflies, Terrobittacus rostratus sp. nov. and Terrobittacus angustus sp. nov., are described and illustrated from Yunnan, southwestern China, increasing the species number of Terrobittacus Tan & Hua, 2009 to six. Terrobittacus rostratus sp. nov. differs from its congeners by wings devoid of markings and epandrial appendages slightly longer than half the length of the gonocoxites. Terrobittacus angustus sp. nov. can be recognized by wing markings along R5 distally. A key to species of the genus is updated to include the two new species.


Introduction
Bittacidae Handlirsch, 1906, a cosmopolitan family of Mecoptera Packard, 1886, is peculiar for the adults having three pairs of raptorial legs, each with a grasping structure formed by the fourth and fifth tarsomeres (Tan & Hua 2008).They usually use their prehensile tarsi to hang themselves from the edge of leaves or twigs of plants; therefore, they are commonly called hangingflies (Byers 2002).The bittacids are mostly found in moist, shady woodlands and have strict habitat requirements (Setty 1940;Byers & Thornhill 1983).During mating, the male frequently provides an insect prey as a nuptial gift to the female, and twists his abdomen temporarily up to 180° to form a belly-to-belly hanging copulation position with the female (Gao & Hua 2013).
The genus Terrobittacus is endemic to China -it is known from the Shaanxi, Henan, Hunan, Guizhou, and Fujian provinces -and has Bittacus implicatus Huang & Hua in Cai et al., 2006 as its type species.Herein, two undescribed species of Terrobittacus from Yunnan, southwestern China, are described as new to science, thereby increasing the species number of Terrobittacus to six.A key to species of the genus is updated to include the two new species.

Material and methods
Type specimens were collected from montane areas in Yongde County, Yunnan Province, and are deposited in 75% ethanol at the Entomological Museum, Northwest A&F University, China (NWAU).
Specimens were observed under a Nikon SMZ1500 microscope.Photographs were taken with a Nikon D7000 digital camera, and stacked with Zerene stacker (version 1.04) software.For scanning electron microscopy (SEM), the samples were dehydrated in a graded ethanol series, replaced by tertiary butanol, dried in a CO 2 critical-point dryer, sputter-coated with gold and examined under a Hitachi S-3400N scanning electron microscope (Hitachi, Tokyo, Japan) at 15 kV.The measurements were obtained with a vernier caliper, and are presented as mean ± SD (standard deviation).

Abbreviations
The following abbreviations are used in measurements:

Diagnosis
The genus can be recognized by the following characters: 1) wings with one pterostigmal cross-vein; 2) tarsomere IV with one spine on each side; 3) male epandrial appendages distinctly shorter than half the length of the gonocoxites, except for T. rostratus sp.nov.with epandrial appendages slightly longer than half the length of the gonocoxites; aedeagal lobes small and acute; tergum X strongly vestigial dorsally; sex pheromone glands single-lobed; 4) the two halves of the subgenital plate almost fused completely in the female.

Diagnosis
The new species differs from its congeners by the following characters: 1) wings hyaline without clouded markings; 2) male epandrial appendages boot-shaped in lateral view, upper branch of proctiger broad with two round lateral flanks and a beak-like apex; 3) female subgenital plate black basally, yellowish brown distally, and with a narrow membranous line mesally.

Etymology
The specific epithet is derived from the Latin 'rostratus' (beak-shaped), referring to the beak-shaped upper branch of the proctiger in the male.
Head.Vertex and frons yellowish brown; clypeus lighter than frons; genae pale; labrum yellowish brown, darker basally and laterally; maxillary and labial palps dark brown; fifth segment of maxillary palp slightly longer than fourth (Fig. 1B).Ocellar triangle black; three ocelli almost equal in diameter; median ocellus accompanied with two bristles.Antennae filiform and ciliated; scape and flagellum dark brown, pedicel pale brown; flagellum with distinct segments basally and obscure beyond 13 th segment.
tHorax.Pronotum black, with two long setae on anterior margin, and a few setae on posterior margin.Anterior two-thirds of mesonotum black, remaining part and metanotum unevenly brown; meso-and metascutellum each with two long black setae (Fig. 1C).Pleura unevenly pale brown.Legs yellowish brown, except coxae pale brown, femora and tibiae darker apically (Fig. 1A); fourth tarsomere with one spine on each side; hind basitarsus longer than second and third tarsomeres together.Wings.Forewing membrane hyaline and tinged with yellowish brown; pterostigma brown; apical margin slightly infuscate; thyridium at FM conspicuous; two nygmata each in cells R 4+5 and 1R 5 ; one Pcv; Sc ending beyond the level of FRs; Cuv near level of FM; CuA ending slightly beyond Sc terminus, CuP terminating near level of Scv; Av absent, 1A terminating beyond the level of ORs; apical crossveins roughly arranged in three lines.Hindwings similar to forewings, but Sc terminating at level of midpoint between ORs and FRs; 1A coalesced with CuP subbasally; apical cross-veins fewer than those of forewings (Fig. 2).abdoMen of Male.Terga II-VIII light brown to dark brown, each with a black narrow antecosta; tergum VIII emarginated on posterior margin.Sterna II-VIII pale to dark brown, sternum IX lighter than sternum VIII.Sex pheromone glands single-lobed, each at intersegmental areas between terga VI−VII and between terga VII−VIII (Fig. 3A).Epandrial appendages (tergum IX) yellowish brown, slightly longer than half the length of gonocoxites, boot-shaped in lateral view, with basal third broad and distal two-thirds narrowed toward rounded apex; inner surface with two patches of small black spines each at apex and dorsal process (Fig. 3B-C), and margin from dorsal process to apex also with sparse spines.Tergum X strongly vestigial dorsally with two slender lateral plates extending to base of lower branch of proctiger.Upper branch of proctiger flat, strongly sclerotized with two broad lateral flanks bearing scattered setae, apex curved caudoventrad into a beak; lower branch of proctiger shorter than upper branch, curved downward and tapering apically (Fig. 3D).Cerci conical, almost one-third as long as gonocoxites (Fig. 3A).Gonocoxites yellowish brown, caudal portion with a pale U-shaped membranous area (Fig. 3E).Gonostyli stout basally, distal portion curved cephalad and tapering toward apex.Aedeagus broad basally, with two aedeagal lobes acute and median penisfilum coiled greatly (Fig. 3A, E). abdoMen of feMale.Terga II-IX yellowish brown or unevenly brown, each with a narrow black antecosta.Sterna II-VII yellowish brown, or pale in sterna II-IV and unevenly dark brown in sterna V-VII.Subgenital plate black basally, yellowish brown distally (Fig. 4A), and with a rather narrow membranous line mesally, which is broadened at distal half (Fig. 4B); a pair of acute processes each  projecting from lateral margins distally, and extending to anterior edge of tergum IX; distal portion of subgenital plate with long thick setae directed caudad (Fig. 4A-B).Tergum X yellowish brown, extending ventrad.Supraanal plate and subanal plate truncated apically.Cerci setose, slightly longer than supraanal plate.

Distribution
Yunnan Province, China.

Remarks
The new species differs from other species of Terrobittacus in its male epandrial appendages, which is slightly longer than half the length of the gonocoxites.
Terrobittacus rostratus sp.nov.resembles T. longisetus and T. implicatus in general appearance, especially the hook-like proctiger in the male genitalia.However, it can be separated from the latter two species by its boot-shaped epandrial appendages.In addition, wings are devoid of markings in T. rostratus sp.nov., but have clouded markings in the latter two species.Females of T. rostratus sp.nov.can also be differentiated from congeners by the unique coloration of its subgenital plate, which is black basally and yellowish brown distally.

Diagnosis
The new species is distinguished from its congeners by the following characters: 1) wings with a clouded brown fleck along R 5 distally; 2) male epandrial appendages narrow, with small black spines on inner  surface of rounded apex; 3) female subgenital plate with a triangular membranous area basally and deeply cleft distally, two black sclerotized carinae at anterior portion.

Etymology
The specific epithet is derived from the Latin 'angustus' (narrow), referring to the narrow shape of the epandrial appendages in lateral view.
Head.Vertex yellowish brown; frons dark brown; clypeus unevenly brown; genae pale yellow; labrum yellowish brown, with lateral edges darker; maxillary and labial palps brown; fourth maxillary palpomere slightly longer than fifth (Fig. 5B).Ocellar triangle black, median ocellus accompanied with two bristles and slightly smaller than others in diameter.Antennae filiform and ciliated; scape and flagellum yellowish brown, pedicel yellowish; flagellum ca 17-segmented and indistinctly segmented apically.unevenly yellowish brown; meso-and metascutellum each with two long setae (Fig. 5C).Pleura unevenly pale brown, with scattered setae.Legs yellowish brown except coxae pale brown, femora and tibiae darker apically (Fig. 5A); fourth tarsomere with one spine on each side, hind basitarsus longer than second and third tarsomeres together.
Wings.Forewing membrane hyaline and tinged with faint yellowish brown, costal margin and apical margin from pterostigma to R 5 slightly darkened; pterostigma conspicuous; brown clouded at ORs, FRs, OM and subdistal CuP, also along apical cross-veins; posterior portion of R 5 with a brown clouded fleck broadening toward apex; two thyridia each at FM and at base of M 4 ; apex of wing almost right-angled and outer margin from R 5 to M 3 straight; one Pcv; Sc ending beyond level of FRs; CuA ending at level of Sc terminus; CuP ending before level of Scv; Cuv before level of FM; 1A ending at level of ORs, or slightly beyond level of ORs; Av absent; apical cross-veins roughly arranged in two lines; cross-veins between M 2 to M 4 transparent.Hindwings similar to forewings, but Sc terminated before FRs, 1A and CuP coalesced subbasally (Fig. 6).abdoMen of Male.Terga II-VIII yellowish brown to dark brown, each with a black narrow antecosta; tergum VIII slightly emarginated on posterior margin.Sterna II-VI pale yellow, sterna VII-IX yellowish brown.Pleura pale.Epandrial appendages rather narrow, clavate in lateral view, broad basally and narrowing toward rounded apex, and distinctly shorter than half of gonocoxites (Fig. 7A); inner surface with a patch of small black spines apically (Fig. 7B).Tergum X vestigial dorsally, with two lateral plates extending to and surrounding bases of cerci.Upper branch of proctiger strongly sclerotized and with two lateral flanks bearing scattered short setae, its apex slightly curved into a hook; lower branch of proctiger curved downward and shorter than upper branch (Fig. 7C).Cerci dark brown and slightly curved apically, slightly shorter than epandrial appendages.Gonocoxites yellowish brown dorsally and dark brown ventrally, completely joined ventrally and with a V-shaped membranous area posteriorly (Fig. 7A, D); in one specimen, gonocoxites separated by a rather narrow membranous area in ventral aspect.Gonostyli setose and tapering toward apex.Aedeagus with two acute aedeagal lobes each projecting a triangular process from anterior margin mesally; penisfilum greatly elongated, coiled (Fig. 7A, D). abdoMen of feMale.Terga II-IX unevenly dark brown, each with narrow black antecosta.Sterna II-VII pale yellow to yellowish brown.Subgenital plate yellowish brown with pale triangular membranous area basally, and deeply cleft apically; lateral margins oval at basal half, and each projecting a slender process extending to anterior edge of tergum IX distally (Fig. 8A); subgenital plate with long thick setae at posterior portion, and a pair of black carinae at anterior portion (Fig. 8B).Tergum X yellowish brown and extending ventrad.Supraanal plate and subanal plate truncated apically with long setae, posterior edge of supraanal plate with a small process mesally.

Distribution
Yunnan Province, China.

Remark
Terrobittacus angustus sp.nov. is similar to T. rostratus sp.nov. in the general coloration and wing venation, but its wings have clouded markings at forks of major veins, along most apical cross-veins and the distal half of R 5 (cf.wings devoid of markings).They can also be readily separated by the external genitalia, for T. angustus sp.nov.has male epandrial appendages clavate in lateral view (cf.epandrial appendages boot-shaped), and female subgenital plate lacking a narrow membranous line mesally (cf.subgenital plate with the membrane in mesal line).

BL
are used in describing wing venation: Av = apical cross-vein between CuP and 1A CuA = anterior cubitus CuP = posterior cubitus Cuv = apical cross-vein between CuA and CuP FM = fork of media FRs = first fork of radial sector ORs = the origin of radial sector Pcv = cross-veins between R 1 and R 2 behind the pterostigma R 1 = first radius Sc = subcosta Scv = cross-vein between distal half of Sc and R 1