Myrmecodema Gebien, 1943

Matthews, Eric G. & Lawrence, John F., 2015, Trachelostenini sensu novo: redescriptions of Trachelostenus Solier, Myrmecodema Gebien and Leaus Matthews & Lawrence, based on adults and larvae, and descriptions of three new species of Leaus (Coleoptera: Tenebrionidae), Zootaxa 4020 (2), pp. 289-312 : 296-300

Myrmecodema Gebien, 1943

( Figs 2 , 4 , 7 , 9 , 17–19 , 37 , 43, 46 , 53, 55 )

Type species: Myrmecodema nycterinoides ( Germain, 1855) by monotypy.

Redescription. Adults. With the characteristics of the tribe. Length 8.0–13.0 mm. Body with fore and hind bodies each elongate oval, altogether 3.3–3.5 times as long as wide, with prothorax only a little narrower than elytral bases, uniformly fuscous. Surfaces glabrous. Head: Basal membrane of labrum very wide. Eyes subcircular or shallowly emarginate anteriorly. Antennae short, reaching only to about middle of prothorax. Antennomeres only a little longer than wide, obconic, not appreciably widening distally, terminal one oval. Mentum transverse, about 3X as wide as long in middle. Prothorax: A little longer than wide, suboval, widest in middle, sides evenly convex, lateral carinae present, not prominent. Procoxal cavities internally closed. Trochantins absent. Pterothorax: Elytra elongate-oval, fused together, discal surfaces smooth or with more or less prominent, complete carinae on odd-numbered intervals. Epipleura not quite reaching elytral apices. Hind wings absent. Legs: Pro-and mesocoxae globose, not very prominent. Tarsi 0.6–0.7 times as long as tibiae. Abdomen: Intercoxal process of first ventrite subparallel, truncate. First 3 ventrites connate. Defensive glands present, small, well separated. Female: Ovipositor greatly elongated, membranous except for baculi and last 2 coxite lobes, with coxite-1 baculi 4 times as long as paraproct baculi. One pair of vaginal sclerites, somewhat triangular and bearing a sharp spine. Spermatheca loosely coiled, branched, attached to anterior part of vagina separately from accessory gland. Sometimes 2 spermathecae present, each attached separately to vagina ( Fig. 2 ).

Adult material examined: Thirty-nine specimens of six species from the Peña collection in FMNH including the holotypes of M. maritima Peña and M. elegantula Peña.

Redescription. Larvae. With the characteristics of the tribe. Dorsal surfaces more or less uniformly yellowish-brown without dark markings. Head with sides distinctly rounded; larger anterior epipharyngeal sensilla ( Fig. 53 ) with anterior 2 very widely separated and distant from the posterior 4, which form a slightly curved, transverse row; posterior sensilla forming an irregular cluster; mandibles tridentate with dorsal and ventral teeth shorter than middle one; gula slightly longer than wide; hypopharyngeal sclerome anteriorly truncate. Prothorax about 0.75 times as long as wide; procoxal area with a distinct, slender, U-shaped sclerite. Legs less than 0.8 times as long as thoracic width and clothed with several stout spines on femur and tibiotarsus. Abdomen about 4.5 times as long as thorax, terga I–VII each with irregular transverse row of pits; tergum IX distinctly longer and slightly wider than VIII, carina distinctly scalloped ( Figs 43, 46 ), surface of concave disc heavily pigmented, more or less covered with dark-rimmed pits extending onto ventral surface; segment X concealed. Spiracles annularmultiforous with a variable number of accessory chambers located around the peritreme ( Fig. 55 ).

Larval material examined: Myrmecodema elegantula Peña. CHILE: RM: Alto Cantillana, 13.i.2000, M. Guerrero coll. ( ANIC). Myrmecodema nycterinoides (Germain) . CHILE: VI: Cachapoal: Res. Nac. Río de Los Cipres, 1.v.2006, M. Guerrero, coll. ( ANIC).

Distribution and habits. Central Chile in the Cordillera Costera Central and Cordillera Andina Central, on stony slopes; larvae are internal feeders in decaying wood ( Vidal & Guerrero 2007).

Discussion. Myrmecodema was described in Physogasterini ( Pimeliinae ) by Germain (1855) but is listed in Misolampini ( Stenochiinae ) in Gebien (1943) and in Cnodalonini (Stenochiinae) by Vidal & Guerrero (2007). The species were revised by Freude (1960) and Peña (1974). The present authors began to suspect that it might be related to Trachelostenus when they saw the descriptions and figures of the larvae in Vidal & Guerrero (2007). Subsequent examination of adults revealed, first of all, that Myrmecodema could not be a stenochiine because it does not have compound sensoria on the antennae, always present in that subfamily ( Doyen 1989). Dissection of females then revealed that the spermatheca is tubular and attached to the vagina separately from the accessory gland ( Fig. 2 sp). In Stenochiinae the spermatheca and accessory gland always form a single structure with the spermathecal part (usually spherical in form) located at the end of the gland ( Tschinkel & Doyen 1980, Doyen 1989). The ovipositor ( Fig. 7 ), which has a very unusual form like that of Trachelostenus as discussed above, plus the presence of vaginal sclerites ( Fig. 2 vs), confirmed the relationship. Also, the aedeagal alae are of the appendiculate type ( Fig. 4 a), unknown in Stenochiinae , and the small, simple defensive gland reservoirs ( Fig. 9 ) are quite unlike those seen in the latter, which have large striated reservoirs.

Figures

FIGURES 1, 2. Female tracts: 1, Trachelostenus inaequalis; 2, Myrmecodema michelbacheri. sp—spermatheca; vs—vaginal sclerite. Scale bars 1 mm.

FIGURES 3 – 5. Aedeagi: 3, Trachelostenus inaequalis with penis extracted; 4, Myrmecodema michelbacheri; 5, Leaus monteithi. a—ala of paramere. Scale bars 1 mm.

FIGURES 6, 7. Ovipositors: 6, Trachelostenus inaequalis; 7, Myrmecodema michelbacheri. cb—baculus of coxite 1; pbbaculus of paraproct. Scale bars 1 mm.

FIGURES 8 – 10. Inside of abdominal ventrites. 8, Trachelostenus inaequalis; 9, Myrmecodema michelbacheri; 10, Leaus tropicalis. Scale bars 1 mm.

FIGURES 17 – 19. Myrmecodema: 17, M. nycterinoides dorsal; 18, M. kochi lateral; 19, M. nycterinoides ventral. Scale bars 1 mm.

FIGURES 37 – 41. Trachelostenine larvae: 37 – 39, head and prothorax, dorsal; 37, Myrmecodema nycterinoides; 38, Trachelostenus inaequalis; 39, Leaus tasmanicus; 40, L. tasmanicus, larval head, dorsal; 41, T. inaequalis, larval head, lateral.

FIGURES 42 – 48. Trachelostenine larvae: 42 – 44: abdominal apex, lateral: 42, Trachelostenus inaequalis; 43, Myrmecodema nycterinoides, 44, Leaus tasmanicus; 45 – 48: abdominal apex, dorsal: 45, Trachelostenus inaequalis; 46, Myrmecodema nycterinoides; 47 – 48, Leaus tasmanicus.

FIGURES 49 – 56. Trachelostenine larvae: 49, Trachelostenus inaequalis, ventral mouthparts and hypopharynx, dorsal. 50 – 51, Leaus tasmanicus, mandibles: 50, right, dorsal; 51, left, dorsal. 52 – 54: labrum-epipharynx, ventral: 52, Trachelostenus inaequalis, 53, Myrmecodema nycterinoides, 54, Leaus tasmanicus. 55 – 56, abdominal spiracle: 55, Myrmecodema nycterinoides. 56, Leaus tasmanicus.