Genus diagnosis. Integument black or piceous, head partially red; body setation usually dense, light or rarely mixed light and black. Size: 8-25 mm (Fig. 1). Head only slightly convex or quite flat, temples more or less parallel, occiput usually rounded, elongate in a single species; red frontal spot in one species more or less extended posteriorly on sides, at least on temples; punctures variously in size and deep. Eleven antennomeres, cylindrical, XI distinctly longer than others; male with or without a modified area (possibly sensory or glandular) on antennomeres III-VII; setation denser and shorter on the last four or five segments. Labrum widely emarginated; mandibles robust and evidently curved; maxillary and labial palpi not modified, last palpomere subsecuriform. Pronotum reniform in one species more conically extended anteriorly, more or less bulged on sides at base, slightly longitudinally depressed in the middle, more or less depressed along the base; prosternum widened on sides; mesonotum not visible dorsally under the pronotum; mesosternum short, wide, anteriorly not modified; metasternum short, wide; elytra usually distinctly setose, imbricate at base, shorter than abdomen, which clearly emerge posteriorly; legs robust and densely setose, tarsomeres elongate, not modified in male; metacoxae partially covered by the middle ones; spurs of pro- and mesotibiae both slender and pointed, the external spur of metatibiae widened and spoon-like, the inner one stick-like; claws smooth. Abdominal tergites broadly sclerotized; sternites not modified; posterior margin of the male penultimate sternite sinuate in the middle, that of the last one deeply V-incised in the middle, rounded in female. Male gonostyli in lateral view more or less clylindrical in the basal half, with apical lobes more or less narrowed and with short setae; phallobase short, usually wide in dorsal view; aedeagus with two ventral hooks or only with one in two species (T. chrysocomus, T. conicicollis).
Trichomeloe belongs to the subfamily Meloinae because of the larval characters (see Bologna and Pinto, 2001) and the mouthparts, claws and male genitalia structure of adult (Bologna, 1991). Larval characters are similar to those of several genera referred to the Lyttini, one lineage which, according to morphological (Bologna and Pinto, 2001) and molecular (Bologna et al., 2008) analyses seems to be polyphyletic. The real phylogenetic affinities of Trichomeloe relative to other genera of Lyttini remain uncertain, as discussed by Bologna (1988, 1989). This genus has some adult derived features (e.g. wingless, brachyelytrous) similar to those of the Mediterranean genus Berberomeloe Bologna, 1989; in common with this genus has also some characters of the first instar larva (Bologna and Pinto, 2001). We are inclined to consider these characters as indicative of relationships between these two genera.
The genus Trichomeloe is phenetically similar to Meloe, but is easily distinguishable by the diffuse setation on the whole body (character present only in few subgenera of Meloe), the reniform pronotum (feature in common to some Meloe (Eurymeloe) only), the presence of a more or less extended red spot on the head. In the subfamily Meloinae, as well as in Tetraonycinae and Nemognathinae, repeated phenomena of converging brachyelytry – with or without associated wingless – evolved in several genera. Some species were originally referred to Meloe Linnaeus, 1758 and afterwards to the following genera: Berberomeloe Bologna, 1989, Lyttomeloe Denier, 1920, Parameloe Denier, 1933 (tribe Lyttini), Pseudomeloe Fairmaire and Germain, 1863 (tribe Pyrotini), Cordylospasta G. Horn, 1875, Megetra LeConte, 1859, Cysteodemus LeConte, 1851 (tribe Eupomphini), Pseudabris Fairmaire, 1894 (tribe Mylabrini), Physomeloe Reitter, 1911 Oreomeloe Tan, 1981 (tribe Meloini), Meloetyphlus Waterhouse, 1872 (tribe Tetraonycini), Allendesalazaria Martinez de la Escalera, 1910, Sitarobrachys Reitter, 1883 (tribe Nemognathini), etc.
An annotated catalogue of the species, and the description of two new species, namely T. mesopotamicus n.sp. and T. syriacus n. sp., are reported in Appendix I.
Keys to the species (for both males and females) are reported in Appendix II.
The examined material is preserved in the collections listed in Appendix III, with associated acronyms reported in the text.