Terrobittacus implicatus (Huang and Hua, 2006) Tan & 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 : 2941-2945

Terrobittacus implicatus (Huang and Hua, 2006) , comb. nov.

( Figures 1–4 ) Bittacus implicatus Huang and Hua in Cai et al., 2006: 128, fig. 2 (type locality: Nanzheng , Shaanxi) .

Redescription

Body relatively small in size, 11 mm long; forewing 15.3–15.5 mm long, 3.8–4.1 mm wide. Hindwing 13.0– 13.6 mm long, 3.0– 3.5 mm wide.

Head. Vertex and frons yellowish brown; rostrum yellowish brown medially and darker laterally; maxillary and labial palps yellowish brown; fifth segment of maxillary palp slightly longer than the fourth. Antennae yellow, about 5.0 mm long; flagellum filiform and ciliated, with about 17 flagellomeres, distal part segmented indistinctly. Three ocelli almost similar in size, relatively small; ocellar triangle black.

Thorax. Pronotum brown; two long black setae on the anterior margin, and two to four setae on the posterior margin. The anterior two-thirds of mesonotum unevenly black-brown with a pale brown median streak; the remaining portion and the metanotum pale brown. Pleura and legs yellowish brown; femora and tibiae with dark apices; apical tibial spurs almost equally long; tarsomere IV with only one spine on each side; hind basitarsus relatively short, slightly longer than the length of tarsomeres III and IV combined.

Wings ( Figure 1 ). Forewing hyaline with faint yellowish tinge; pterostigma dark brown; four distinct dark brown clouding flecks each at ORs, FRs, OM and subdistal CuP. One Pcv; Sc ending beyond the level of FRs; Scv very near the ending point of Sc, beyond FRs; Cuv approaching the level of FM; Av varying from absent, present or vestigial to a small section in different individuals. 1A terminating before the middle point of FRs and ORs; apical cross-veins arranged roughly in two lines, along cross-veins 1s and 2s, respectively. Hindwing similar to forewing, but Av absent; Sc ending beyond the level of ORs, far before FRs; Scv before the middle point of ORs and FRs.

Abdomen of male. Terga II–VIII yellowish brown; each with narrow black antecosta; posterior margin of tergum VIII emarginate in V-shape. Sex pheromone glands single-lobed, present at the membranous areas both between terga VI–VII and VII–VIII ( Figure 4C ). Epandrial appendage yellowish brown, very small, shorter than half length of gonocoxites, roughly triangular in shape from lateral view; dorsal margin distinctly inclined upwards with numerous long setae; ventral margin straight, with apex protruding ventrad into a large denticulate process ( Figure 2A ), inner surface of the process bearing numerous long setae; apical margin slightly curved with long hairs; the inner surface of the epandrial appendage thickened, bearing a patch of small black spines ( Figure 3C ); the spine conical, with radial grooves ( Figure 3D ). Tergum X vestigial dorsally into a simple transverse plate with its posterior corners narrowly extending posteroventrad and then curved dorsad around base of cercus, forming a large roughly quadrangular hairless area mesal to cercus ( Figure 2A ). Upper branch of proctiger strong sclerotized dorsolaterally, protruding between bases of epandrial appendages, with apex curved caudoventrad into a hook, shaped like rostrum of parrot ( Figure 2A ); lower branch of proctiger very short, broad basally and tapering toward apex. Cerci rather short, only about one-quarter length of gonocoxites. Gonocoxites dark brown, very large, posteroventrally rounded with a V-shaped pale area medially ( Figure 2A ). Gonostylus short, mesally curved with apex bluntly rounded, clothed with numerous brown setae ( Figure 3E,F ). Aedeagus slender, with greatly coiled elongate penisfilum and two small acute basal lobes ( Figure 3E ).

Abdomen of female. Terga II–IX yellowish brown; terga III–IX each with narrow black antecosta, tergum IX the longest and broadest. Subgenitale roughly rectangular, strongly sclerotized and black along the basal half of midventral line; a pair of slender processes projecting back from posterior corner ( Figure 2B ); subgenitale broad with a number of black stiff setae; the two halves almost completely fused, with a very narrow suture ( Figure 2C ). Tergum X pale brown, narrow, hardly extending ventrad ( Figure 2D,E ). Supraanale, subanale and cerci brown; subanale and supraanale short and broad, equal in length, truncate apically; cerci slender, a little longer than supraanale ( Figure 2D,E ). Spermatheca pear-shaped, with a short rostrum ( Figure 2F ).

Material examined

Holotype male, China: Shaanxi: Nanzheng Forest Park (altitude 1500 m), 12 August 2004, coll. Lijun Cai; paratypes 9 females 17 males, 1–12 August 2004; same data as holotype. 15 males 42 females, 4–7 August 2007, 16 males 24 females, 1 July to 13 August 2005, Liping Forest Park, Nanzheng, Shaanxi, coll. Jiangli Tan and Lijun Cai. One male, 24 June 2007, Mount Nangongshan , Lan’gao, Shaanxi, coll. Baozhen Hua and Jiangli Tan. Preserved at the Entomological Museum, Northwest A & F University, Yangling, Shaanxi, China ( NWAU).

Biology

The adults of T. implicatus emerge from early July to mid-September in the field. As a dominant species of hangingflies in the Daba Moutains, Shaanxi, 57 adult individuals were captured and reared in August 2007, and more than 400 eggs were obtained. Females simply drop eggs singly and randomly to the ground. The first larva hatched on 31 March 2008 in the laboratory and was reared to its fourth instar. Unfortunately, we failed to get its pupa. Terrobittacus implicatus is a univoltine species of hangingflies, completing one generation per year and overwintering as diapausing eggs on the ground. The duration of the egg stage including the diapausing period is about 240 days.

Egg ( Figure 3A ). The egg is subspherical in shape, 0.7 mm in equatorial diameter and 0.8 mm in polar diameter ( Figure 3A ); pale with yellowish tinge when newly deposited but turning dark brown several hours later. The egg surface is tough, especially at both polar areas, and covered with numerous granules; it resembles a terrestrial globe in shape with six distinct grids of latitudes. The chorion was observed to be decorated with a hexagonal network when the granules were removed ( Figure 3B ).

Larva ( Figure 4A, B ). The larva is eruciform, with three pairs of thoracic legs and eight pairs of abdominal prolegs. The body is cylindrical, generally creamy-white with mandibles reddish brown; the head is hypognathous with two reddish brown eyes and a large median ocellus, bearing pairs of clavate setae furnished with fine hairs. The somites possess rows of fleshy, branched protuberances, terminating in dark brown acerate setae; dorsal protuberance distinctly long, about twice as long as its apical long setae in the first instar. Telson ends in a protrusile sucker. Measurements (at the beginning of each instar): body length 3.8, 6.0, 8.2, 12.5 mm, respectively; width of head capsule about 0.63, 0.81, 1.0, 1.33 mm; length of mesothoracic dorsal protuberance 0.87, 1.07, 1.5, 1.6 mm, with its apical setae 0.33 mm long in all instars.

The larva is similar to that of Bittacus in appearance, but can be easily distinguished from the latter by the distinctly long dorsal protuberance, apical setae of the branched protuberance dark brown, conspicuously acerate rather than clavate.

Remarks

The original description was published in Chinese though it was accompanied by an English abstract. Here we make a redescription and re-illustration of males according to the specimens kept in 75% alcohol. The female is described and illustrated for the first time. The immature stages and biology are also reported for the first time.

Figures

Figure 1. Terrobittacus implicatus, comb. nov., male adult, lateral view.

Figure 2. Genitalia of Terrobittacus implicatus, comb. nov. (A) Terminalia of male, lateral view; (B) abdominal end of female, lateral view; (C) subgenitale of female, ventral view; (D, E) abdominal segment X, dorsal and ventral views, respectively; (F) spermatheca.

Figure 3. Fine structure of Terrobittacus implicatus, comb. nov., scanning electron micrographs. (A) Egg, showing the terrestrial globe shape with grid of latitudes on the chorion, scale bar = 100 µm; (B) part of chorion with the surface granules removed, showing the polygonal network, scale bar = 10 µm; (C) right epandrial appendage, inner aspect, showing the patch of spines, scale bar = 100 µm; (D) magnification of a spine on the inner surface of epandrial appendage, scale bar = 5 µm; (E) male genitalia, dorsocaudal view, scale bar = 200 µm; (F) magnification of left gonostylus, scale bar = 50 µm.

Figure 4. Terrobittacus implicatus, comb. nov. (A) First instar larva; (B) second instar larva; (C) male adult, showing the rounded, single-lobed sex pheromone glands; (D) female adult is laying an egg.