Enigmocephala, Rédei, Dávid, 2007

Rédei, Dávid, 2007, A new genus of tribelocephaline assassin bugs from Borneo (Hemiptera: Heteroptera: Reduviidae), Zootaxa 1465, pp. 47-53 : 48-51

Enigmocephala gen. n.

Diagnosis. Recognized among other genera of Tribelocephalinae by the combination of the following characters: labium very robust, being widest near middle of second visible segment and gradually narrowed apicad; apical labial segment bearing finger-like projections apically; legs short, stout, tibiae strongly curved apically; and abdominal sternites nearly entirely fused.

Description. Based on an apterous female.

Body ( Fig. 1 ) robust, heavily sclerotized, with rather short appendages; body surface nearly bare, with short, rather stiff, adpressed pilosity on legs and several distinct areas bearing short, dense pubescence. Head ( Figs. 2–5 ) oval, furnished with a transverse, collar-like pubescent area at base, provided with a pair of longitudinal fringe-like structures composed of long setae on ventral surface; with a deep interocular furrow surrounding a transverse, oval area between eyes; with two tubercle-like elevations in front of interocular furrow; area anterior to antenniferous tubercles strongly declivent, anteriorly flat, clypeus distinctly elevated, laterally somewhat flattened, declivent anteriorly; neck narrow ( Fig. 4 ). Eyes relatively small, flat, barely projecting laterally from surface of head. Antenna ( Fig. 2 ) rather short; scape strongly widened, distinctly shorter than head, bearing a longitudinal pubescent area laterally; pedicel distinctly longer than scape, cylindrical, strongly curved near base; flagellum gracile, subdivided into six secondary segments (apparently basiflagellomere into two and distiflagellomere into four). Labium ( Figs. 3–6 ) very robust, with three visible segments (corresponding to segments II–IV), first visible segment (II) laterally flattened in basal half, wide and cylindrical in apical half, extending to about middle of eyes; second visible segment (III) laterally strongly flattened except its base, very strongly narrowing apically, extending between fore coxae; third visible segment (IV) extremely short, with short, dorsal and ventral apical projections ( Fig. 6 ). Thorax with more or less wide stripes or patches of dense pubescence between tergum and pleuron, between pleurites, and between metapleura and abdomen ( Fig. 3 ). Pronotum ( Figs. 2, 3 ) transverse, bearing wide, rounded carinae and tubercles, with an anterior transverse pubescent area continuing onto anterior margin of propleuron. Meso- and metathoracic wings absent. Legs as in Figs. 7–9 , rather short; femora robust, distinctly constricted before apex, with two ventral longitudinal pubescent areas; fore femur with one dorsal longitudinal pubescent area; tibiae strongly curved apically; tarsi two-segmented, segment I short; pretarsi with pair simple subequal claws. Abdomen nearly circular in dorsal aspect ( Fig. 1 ), strongly convex ventrally ( Fig. 10 ); dorsal laterotergites extremely wide; tergites I+II and III fused, together bearing pair large, oval pubescent areas; intersegmental suture between tergites IV and V strongly curved anteriad medially; a row of short carinulae present along anterior border of tergites IV–VII; orifices of dorsal abdominal glands present at posterior border of tergites IV and V; sternites largely fused, only shallow sulci present between them except between sternites VI and VII medially ( Fig. 10 ). Spiracles of segment I dorsal, located on distinct elevations of fused tergites I+II and III ( Fig. 2 ); spiracles of segments II–VII ventral ( Fig. 10 ); an additional pair of spiracles on separated sclerites derived from segment VIII ( Fig. 12 ). Female genitalia determined mostly by tergite IX and gonocoxites VIII forming together a nearly vertical surface ( Figs 10–12 ); tergite IX elongate, tongue-shaped, slightly narrowing apically; gonapophyses small.

Type species. Enigmocephala deinorhyncha sp. n., present designation.

Etymology. The generic name from the Greek αɭνɭγμα (latinized as enigma) ‘riddle’ and κεφαλη (latinized as cephale) ‘head’, the latter referring to Tribelocephala , the type genus of the subfamily Tribelocephalinae. Gender feminine.

Distribution. Known exclusively from Borneo.

Subfamily and tribal placement. Although this new genus bears superficial resemblance to Ectrichodiinae (such as the heavily sclerotized body, the secondarily subdivided antennal flagellum, and the presence of short longitudinal carinulae at the anterior margin of the abdominal sternites), Enigmocephala clearly belongs to Tribelocephalinae because of the following characters: third visible labial segment (IV) strongly shortened (synapomorphy of Tribelocephalinae); presence of basal collar-like pubescent area and a pair of longitudinal fringe-like structures on ventral surface of head (apomorphy occurring in many genera of Tribelocephalinae); absence of fossula spongiosa (invariably present on fore and mid legs in Ectrichodiinae ); labrum not subdivided (subdivided in Ectrichodiinae except in Ectrichodiella Fracker & Bruner, 1924 and Schuhella Dougherty, 1995); and ocelli absent (synapomorphy of Tribelocephalinae).

The fore wing venation is currently the single recognized character for differentiating Tribelocephalini from Opistoplatyini ( Villiers 1943, Maldonado Capriles 1996). This character cannot be examined in the apterous holotype designated below for the new species of this genus. However, the new genus is very similar to the Bornean genera Gastrogyrus Bergroth, 1921 and Matangocoris Miller, 1940, both clearly belonging to Tribelocephalini, in the anteriorly declivent head, the presence of a basal pubescent area and ventral fringelike pilosity of the head, and the robust labium. Some of these may be synapomorphies for the presumably monophyletic group composed of these genera (probably also Afrodecius Jeannel, 1911). Therefore, Enigmocephala is placed in the tribe Tribelocephalini.

Differentiating from similar genera. Enigmocephala is unique within Tribelocephalinae with respect to the characters mentioned under the Diagnosis except the tendency towards the fusion of the abdominal sternites which occurs at least in Afrodecius Jeannel, 1919 and Homognetus Bergroth, 1923. As pointed out above, the new genus is similar in several respects to Gastrogyrus and Matangocoris. However, in the latter two genera the second visible labial segment is strongly narrowed in its apical 3/5–1/2 part, and the third visible segment is simple. In Gastrogyrus, the antennal flagellum is not secondarily fragmented ( China & Usinger, 1949), and furthermore the basiflagellomere is much wider than the distiflagellomere. In Matangocoris, setae of both the basal pubescent area and the ventral fringe-like pilosity of the head are very short.

The projection-bearing third visible (IV) segment of the labium of Enigmocephala is unique within Reduviidae , even within Heteroptera. The only other genus with a more or less similar, strongly modified apical labial segment is Afrodecius. However, in the latter, two beak-like, apparently movable lobes are present, both most probably having originated from segment IV. The exact origin and functional anatomy of these structures requires further study.

The genera of the tribe Tribelocephalini can be distinguished with the key below. Acanthorhinocoris Miller, 1940 was placed to Tribelocephalini by Maldonado Capriles (1990, 1996). However, according to information received from M.D. Webb (The Natural History Museum, London), a distinct Cu-PCu cross vein is present in this genus; therefore, Acanthorhinocoris is hereby removed from Tribelocephalini and placed in Opistoplatyini.

Figures

FIGURE 1. Enigmocephala deinorhyncha gen. n., sp. n., female holotype.

FIGURES 2 – 6. Enigmocephala deinorhyncha gen. n., sp. n., female holotype. 2, head, thorax and base of abdomen, dorsal view, 3, same, lateral view, 4, head, dorsal view, 5, same, anterior view, 6, apex of labium, lateral view. Scales in mm.

FIGURES 7 – 12. Enigmocephala deinorhyncha gen. n., sp. n., female holotype. 7, right fore leg, 8, right mid leg, 9, right hind leg, 10, abdomen, lateral view, 11, apex of abdomen, lateral view, 12, same, posterior view. Scales in mm.