Hesperinus WALKER, 1848

Papp, L., 2010, A Study On Hesperinus Walker With Description Of A New Species (Diptera: Hesperinidae), Acta Zoologica Academiae Scientiarum Hungaricae 56 (4), pp. 347-370 : 348-350

Hesperinus WALKER, 1848

Type species: Hesperinus brevifrons WALKER, 1848 (orig. des., mon.).

Gender: masculine.

Spodius LOEW, 1858 ; a junior subjective synonym. Type species: Spodius imbecillus LOEW, 1858 (orig. des., mon.).

This is the only genus of the family Hesperinidae , consequently its features are characteristic also for the family.

The terminology for the structure of the head follows MATILE (1990). For detailed morphology of the family (i.e. for the only genus Hesperinus ) see KRIVOSHEINA (1997).

Head comparatively small, frons broad also in males, eyes oval, dichoptic, ocelli comparatively large, each on small tubercles. Eye facets of equal size. Scape and pedicel sub-globular (only slightly longer than broad) or pedicel cylindrical. Antenna with 10 flagellomeres ( Fig. 43 , photo) in H. imbecillus , and also in H. brevifrons (see HARDY 1981: fig. 2). Tenth flagellomere rounded ( H. imbecillus , Figs 2–3 ) or elongated. Distal dorsal corners of first flagellomere and that of the next ones are distinct ( H. imbecillus , Fig. 1 ) or indistinct ( H. graecus , Fig. 45 ). Flagellomeres longer (male) or short (female).

Mouth parts distinct, comparatively well-developed. Palpus usually longer than head, four-segmented (see e.g. MOHRIG et al. (1975): figs 2c, 3b, 4b,c): basal segment being the shortest in male, comparatively longer in female, second segment the thickest in female, elongated in male, third and fourth segments elongated, particularly so for the fourth.

Pronotal lobes of thorax small but prescutum separated from mesoscutum by a distinct though shallow transverse groove behind head. Scutellum small, subscutellum indistinct (contrary to Pachyneura ).

Wing membrane not patterned but with distinct or indistinct pterostigma. No strong costal fringe. Costa reaches 1/3 to 1/2 of distance between R 5 and M 1, in cases ends not far from R 5 (wing vein terminology follows KRZEMIŃSKI & EVENHUIS 2000). Radial veins R 1 and R 5 dorsally with long setae. Vein R 4 long and sinuous ( KRIVOSHEINA 1997: fig. 4), with some dorsal setae (seldom bare). M 1, M 2, M 3 with dorsal setae, more rarely setae also on apical part of Cu 1. Cross-vein M 3 -Cu 1, M 3 longitudinal vein and basal part of M 3 meet in a point, where smallest angle is on M 3, largest angle formed by the basal part and cross-vein. M 1 -M 2 and R 5 (more precisely: Rs) rather far from each other, i.e. R-M cross-vein long. Cu 2 distinct and runs rather far from Cu 1 and ends at the strongest curvature of Cu 1. A 1 long, reaching wing margin but A 2 indiscernible(reduced to alar base). No alula, sub-basal edge of wing bears long setulae.

Halter long, stalk of halter with hair all along. Knob flattened.

Legs long, coxae medium-long, subequal. Femoral and tibial setulae fine and dense, and not arranged in rows. Tibial spurs 1+2+2, more or less developed and hairy. Fore tibia without an emarginated area. Metatarsi long, almost as long as other tarsomeres combined. No anterior or posterior combs of small thornlets at apices of tibiae. Tarsal claws simple, short, pulvilli and empodium minute.

Abdomen very long with 8 normal abdominal segments, the 8th can be named as postabdominal. In each segment tergite and sternite almost meet laterally, i.e. intervening membranous area rather small. Spiracle pairs 1–7 are situated in membrane. Tergite 8 and sternite 8 have species-specific shape and setosity. Epandrium ( Figs 6 , 14 , etc.) usually simple but may be species-specific. Left and right gonocoxites fused medially ( Figs 18 , 36 , 52 ) into a ventral scoop-shaped structure, whose ventral caudal edge dorsally curved and so closing genital cavity caudally. The dorsal part of gonocoxites with the medio-cranial gonocoxal apodemes, under the epandrium (gonocoxal apodemes are linked to the inner genitalia through connections to parameres). Dorso-caudally gonocoxites form a pair of closed sclerites with a hole, which embrace base of gonostyli ( Figs 18 , 36 , 52 ). Gonostylus is shoe-lift–shaped, i.e. concave except for a basal part proximal to sub-basal process; the concavity is more or less strong in males of the different populations of H. imbecillus . Dorsal edge with a subapical usually broad medial lobe and a sub-basal process ( Figs 8 , 15 , etc.). The latter seems double in cases, when ventral edge of gonostylus bulging below the process. Parameres, phallus and ejaculatory apodeme form the intricate inner genitalia, where phallus is minute (see also SINCLAIR 2000: figs 2.8–11 for H. brevifrons WALKER ). Also the form and setosity of the cerci and hypoproct may show specific features.

The larvae and pupae of H. rohdendorfi KRIVOSHEINA et MAMAEV, 1967 were found in decaying wet logs of deciduous trees in the Russian Far East. This is the only reliable record of their life habits. The adults of H. imbecillus were found close to mountain streamlets (its flightless female on soil only) during spring months.

No described fossil of Hesperinidae has been found until rather recently. SKARTVEIT (2009) described three species of Hesperinus from Baltic amber (early Eocene) but the minimum age of the stem species has not been known. For instance, that of the Pachyneuridae is from the Upper Jurassic (Tithonian) ( EVENHUIS 1994). There is a single genus known in the family; hitherto six species of peculiar distribution have been known.

There is one species each in the Nearctic and the Neotropical regions, incl. the type species, H. brevifrons WALKER, 1848 ( Canada and U.S.A. (incl. Alaska )), and H. conjungens SCHINER, 1968 ( Brazil). In the Palaearctic region there is one species H. imbecillus ( LOEW, 1858) in Europe, see below. In addition, several specimens of a Hesperinus species were captured in the North Caucasus (Krasnodarskiy kray). The identity of the latter specimens was established now: those represent another (i.e. a new) species (see PAPP & KREIVOSHEINA 2010).

Three species ( H. cuspidistylus HARDY et TAKAHASHI, 1960 , H. nigratus OKADA, 1934 and H. rohdendorfi KRIVOSHEINA et MAMAEV, 1967 ) have been known in the Russian Far East (Primorskiy kray, Kuril Is.) and Japan (Hokkaido, Honshu) (see KRIVOSHEINA & MAMAEV 1986). Some specimens of the latter two species are preserved in the HNHM and have also been studied there.

Specific differentiating features are summarised in the key below.

Figures

Figs 40–43. Hesperinus imbecillus (LOEW), a male from Bulgaria. 40 = gonostylus, in a subdorsal view, which is perpendicular to medial process, 41 = sub-basal process of gonostylus, in a view perpendicular to it, 42 = contours of gonostylus, in widest view, 43 = ejaculatory apodeme, dorsal view.

Figs 1–3. Hesperinus imbecillus (LOEW), antenna of a male specimen from the Tordai-hasadék: 1 = 1st flagellomere, 2 = terminal (10th) flagellomere,medial (inner) view,3 =same, lateral (outer) view.

Figs 44–51. Hesperinus graecus sp. n., holotype male.44 = outline of antenna, 45 = 1st flagellomere, 46 = terminal (10th) flagellomere, 47 = tergite 8, 48 = sternite 8, 49 = epandrium, dorsal view (outset: its microtrichia in higher magnification), 50 = gonostylus, in a subdorsal view, which is perpendicular to medial process, 51 = contours of gonostylus,in widest view.Scales: 1.0 mm for Fig.44, 0.4 mm

Figs 4–11. Hesperinus imbecillus (LOEW), postabdomen and genitalia of a male from “Styria inf.”: 4 = tergite 8, 5 = sternite 8, 6 = epandrium, dorsal view, 7 = ejaculatory apodeme, dorsal view, 8 = gonostylus, in a subdorsal view, which is perpendicular to medial process, 9 = contours of gonostylus, in widest view, 10 = sub-basal process of gonostylus, in a view perpendicular to it, 11 =

Figs 12–17. Hesperinus imbecillus (LOEW), a male from the Papuk Mts, Croatia. 12 = tergite 8, 13 = sternite 8, 14 = epandrium, dorsal view, 17= gonostylus, in a subdorsal view, which is perpendicular to medial process, 16 = contours of gonostylus, in widest view, 15 = sub-basal process of gonostylus, in a view perpendicular to it. Scales: 0.4 mm for Figs 12–13, 0.2 mm for 15–16, and Fig 14, respec-

Figs 18–21. Hesperinus imbecillus (LOEW), a male from the Papuk Mts, Croatia. 18 = right gonocoxite and gonostylus in dorsal view, 19 = ejaculatory apodeme, dorsal view, 20 = inner genitalia with fused parameres, ventral view, 21 = proctiger, dorsal view. Scale:0.2 mm for Figs 18, 20–21,

Figs 36–39. Hesperinus imbecillus (LOEW), a male from the Tordai-hasadék, Romania. 36 = left gonocoxite and gonostylus in dorsal view, 37 = ejaculatory apodeme, dorsal view, 38 = proctiger, dorsal view, 39 = inner genitalia with fused parameres, ventral view. Scales: 0.2 mm for Figs 36,

Figs 52–57. Hesperinus graecus sp. n., holotype male. 52 = gonocoxites and gonostyli, full dorsal view, 53 = proctiger, dorsal view, 54 = cercus, hypoproct and membranes, lateral view, 55 = ejaculatory apodeme, dorsal view, 56 = inner genitalia, ventral view, 57 = same, dorsal view (arrow: base of