Melchus Lacordaire

Anderson, Robert S., 2003, Neotropical Dryophthoridae: Redescription of the Genus Melchus Lacordaire with Description of Daisya Anderson, New Genus, and Seven New Species (Coleoptera: Curculionoidea), The Coleopterists Bulletin 57 (4), pp. 413-432 : 415-416

Melchus Lacordaire

Figs. 1–23

Melchus Lacordaire 1866:300 . Wibmer and O’Brien 1986:364. Alonso-Zarazaga and Lyal 1999:65. Anderson 2002:7, 13.

Type Species. Melchus leprosus Lacordaire by present designation.

Identification. This genus can be characterized by the combination of scutellum rhomboidal in shape, the greatest width at or near the middle ( Fig. 19 ); rostrum more or less straight ( Figs. 11–15 ) with the apical one-half distinctly laterally compressed and ‘‘knife-like’’ ( Figs. 16–17 ); mesepimeron with the dorsal one-half of the anterior face precipitous, broadly abutting the posterolateral margin of the pronotum; antenna with scape shorter than the funicle ( Fig. 18 ); and, tarsus with width of article 3 three to four times width of article 2 ( Fig. 20 ). All species also have fine golden micropilosity surrounding the punctures ( Figs. 1–10 ), each of which also bears a short, robust seta. This pilosity and setation are most evident on the ventral surface of the thoracic sterna and the abdomen but are also present as micropilose nodules on the pronotum and elytra of M. leprosus , M. perplexus and M. onorei ( Figs. 1, 5, 7 ).

Description. Length 7.8–9.5 mm, width 3.7–5.0 mm. Color black or dark reddish brown, with or without vague pale reddish markings or infuscations. Integument dull, punctate throughout. Punctures each bearing a short, robust seta, surrounded by dense golden micropilosity, especially evident on venter of thoracic sterna and abdomen. Rostrum more or less straight, cylindrical basally, markedly laterally compressed and ‘‘knife-like’’ in apical one-half; densely punctate basally, less so apically. Mandibles much taller than long. Peduncle of postmentum rounded, prominent ventrally or not. Antennae inserted subbasally on rostrum, scape shorter than funicle; funicle with articles 3–5 slender, longer than wide; club somewhat elongate, especially basal glabrous part. Pronotum wide, disk flat; lateral margins subparallel in basal one-half, evenly rounded, convergent to apex in apical one-half; basal margin slightly sinuate at middle. Elytra broad, flat; intervals of uniform width, with or without micropilose nodules; striae shallowly impressed. Scutellum rhomboidal, widest at or near middle. Procoxae separated by about width of antennal club; mesocoxae separated by from one-third to two-thirds width of mesocoxa; metacoxae widely separated by about one and one-half to two times width of metacoxa. Prosternum flat, sloping anteriorly between procoxae; prosternal process acuminate. Mesosternal process flat, truncate, very slightly emarginate at apex; mesepimeron with the dorsal one-half of the anterior face precipitous, broadly abutting the posterolateral margin of the pronotum. Metasternum concave at middle, otherwise flat. Pygydium exposed, more or less vertical in orientation in male, slightly more horizontal and prolonged apically in female; flat, punctate throughout, pilose apically. Legs with inner face of each coxa with tuft of long setae; legs each with femur and tibia more or less straight. Tarsus with articles 1–3 with ventral surfaces densely pilose; width of article 3 three to four times width of article 2, wider than long. Male with aedeagus short, slightly to moderately ventrally arcuate, laterally with distinct unsclerotized arcuate line dividing aedeagus into apically narrow dorsal portion and apically broader ventral portion; apex not projected, evenly rounded, subtruncate or very slightly emarginate. Median struts transversely fused for short distance at more or less basal one-quarter, subparallel or divergent to apex. Internal sac with only very long, very fine, narrow median rod, finely bifurcate at extreme apex. Tegminal strut extended slightly beyond apex of internal sac, widest at apex. Tergite 8 somewhat produced and elongate in form, maximum length subequal to or slightly longer than maximum width at base; with long dense setae at apex, apex evenly rounded, slightly produced or subtruncate, very slightly emarginate at middle or not. Paired sclerites of sternite 8 elongate, length two to three times maximum width. Genitalia of female not examined.

Sexual Variation. Only eight male specimens of four species and two females of a fifth species of this genus have been examined. Males bear no remarkable features known to be sexual dimorphic in other Dryophthoridae . The females examined have the pygydium slightly more horizontal in orientation with the apex slightly more prolonged than in males. Another known female specimen, a syntype of M. leprosus , has not been located.

Distribution and Diversity. Costa Rica, Venezuela, Ecuador and Bolivia. There are five known species of the genus Melchus , four of which are described herein. These new species are M. gomezi Anderson from Costa Rica, M. jolyi Anderson from Venezuela, M. perplexus Anderson from Bolivia, and M. onorei Anderson from Ecuador. The remaining species is M. leprosus Lacordaire ; M. umbratilis Lacordaire is transferred to the new genus Daisya Anderson.

Natural History. Adult specimens have been collected in mid-elevation moist tropical forest. No other information is available on the natural history of this genus.

Figures

Figs. 1–10. Melchus species. 1) Melchus leprosus, dorsal view; 2) same, lateral view; 3) M. gomezi, dorsal view; 4) same, lateral view; 5) M. onorei, dorsal view; 6) same, lateral view; 7) M. perplexus, dorsal view; 8) Same, lateral view; 9) M. jolyi, dorsal view; 10) Same, lateral view.

Figs. 11–23. Melchus species. 11) M. leprosus, head, lateral view; 12) M. gomezi, head, lateral view; 13) M. onorei, head, lateral view; 14) M. perplexus, head, lateral view; 15) M. jolyi, head, lateral view; 16) M. onorei, rostrum, dorsal view; 17) M. perplexus, rostrum, dorsal view; 18) M. leprosus, antenna, lateral view; 19) M. gomezi, scutellum, dorsal view; 20) M. gomezi, hind tarsus, dorsal view; 21) M. leprosus, tergite 8 and sternite 8, ventral view; 22) M. leprosus, aedeagus, dorsal view; 23) M. leprosus, aedeagus, lateral view. Scale line ¼ 1.0 mm, except tarsus and scutellum, 0.63 mm.