Melchus jessae Anderson

Anderson, Robert S., 2013, Two new species of Dryophthorinae in the genera Metamasius and Melchus from the Lesser Antilles (Coleoptera: Curculionidae), Zootaxa 3750 (4), pp. 396-400 : 398-400

Melchus jessae Anderson , new species

( Figures 5–8 )

Identification.—Specimens of this species can be recognized by the combination of scutellar shield subcircularrhomboidal (rhomboid but with the exterior angles rounded off) in shape, the greatest width at or near the middle; rostrum more or less straight, cylindrical throughout its length; 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; and, tarsus with width of article 3 three to four times width of article 2. Within the Antillean fauna this species is easily recognizable as no other known Lesser Antillean dryophthorine has a subcircularrhomboidal scutellar shield and raised nodules of small, erect scales on the elytra. Previously, all Melchus species known have been from South America and Costa Rica in Central America.

Description.— Male, 8.5-9.1 mm long; 4.2-4.5 mm wide. Female, 8.1-8.2 mm long; 3.9 mm wide. Color black, body covered with fine golden velvet-like micropilosity except ventrally towards midline and disc of pronotum. Rostrum subequal in length to pronotum; elongate, cylindrical, almost straight, coarsely (male) or finely (female) punctate; base of rostrum slightly expanded in dorsal view, basal expanded area short, about one-fifth total rostral length. Rostrum glabrous ventrally; peduncle flat, bilamellate anteriorly. Scrobe very short, with posterior margin separated from anterior margin of eyes by about one-half width of base of scape. Antennal scape about one-third length of rostrum; club slender, elongate-oval; apical pilose part about one-third to one-quarter length of entire club. Pronotum with lateral margins subparallel in basal one-half, convergent subapically; moderately densely, moderately deeply punctate on flanks and disc; flat to very slightly raised medially at base. Pronotum with length subequal to width. Elytra slightly less than twice length of pronotum; intervals impunctate but with scattered raised nodules of 1-5 small, erect scales; flat, striae distinct, punctures individually indistinct. Scutellar shield subcircular to rhomboidal, slightly wider than long, slightly concave medially. Pygidium flat, oblique in orientation, shallowly regularly punctate, bordered apically by row of short, erect scales. Ventrally with front coxae very narrowly separated by about width of antennal scape at base; prosternum moderately densely, regularly punctate, flat. Lateral portions of meso-, metasternum and ventrites 1 to 5 moderately densely to densely punctate; middle of metasternum and ventrites 2-4 virtually impunctate in female, with few widely scattered small punctures in male, shining; last ventrite flat, apical margin with a few short, erect scales. Legs largely covered with same golden micropilosity as on body; femora clavate, hind femur reaching apex of ventrite 5; inner margins of middle and hind tibiae straight, that of front tibia slightly inwardly curved. Tarsi long and moderately slender, articles 1 and 2 not expanded laterally, article 3 broadly expanded laterally; ventrally articles 1 and 2 with dense fine pilosity in apical one-third, article 3 with dense fine pilosity throughout.

Sexual dimorphism.—In the specimens at hand, males have the rostrum generally more extensively and deeply punctate than in females. The rostra of both sexes are cylindrical throughout their length.

Material Examined.—Male HOLOTYPE labelled “LESSER ANTILLES: St. Lucia / Mon Repos, 6.5 km W Fox Grove Inn / 10-28.VII.07, submontane forest malaises / N13°52.5’ W60°56.4’, 300m / S & J. Peck, 07-53A” (CMNC). Paratypes: 2 males, 3 females. 1 female, St. Lucia, 2000’, Mt. Casteau Rd., 2 mi. N.E. Fond St. Jacques, 9.ix.1986, C.W. and L.B. O’Brien (CWOB). 1 male, St. Lucia, Piton Flore trap site, 532m, 13.9646, -60.9448, 27 June – 0 3 July, 2009, uv light, C.A. Maier and M.L. Gimmel (WIBF 0 59311, WIBF). 1 male, St. Lucia, Mont La Combe trap site, 273m, 13.9209, -60.9592, 11-14 June, 2009, uv light, M.L. Gimmel and C.A. Maier (WIBF 0 59310, CMNC). 1 female, Dominica, Morne Plat Pays, 10.xii.1964, P.J. Spangler, in base Euterpe globosa fronds (USNM). 1 female, Dominica, Boeri Lake Trail, 15.35172N 61.32001W, 6.vi.2011, H.J. Blackburn, on plants along trail (WIBF).

Distribution. — Dominica, St. Lucia.

Taxonomic comments.— The genus Melchus has previously been characterized by the characters listed in the diagnosis of Melchus jessae with the exception of the cylindrical rostrum. The rostra of all previously known Melchus species was distinctly laterally compressed apically and ‘knife-like’ in appearance (Anderson 2003). Placement in Neophrynoides was initially considered for this species but subsequently deemed problematical in that Neophrynoides (represented only by N. luteus ) has a different tarsal structure, the articles (especially article 3) not nearly as wide and much stouter; the length of the scape is much shorter, with the apex of the antennal club different; and the tibiae are stouter with the inner margin sinuate and with a second distinct tooth near the apex giving them a “pincer-like” appearance. Thus, as Melchus jessae agrees with all characters of the genus Melchus except in not possessing a compressed rostrum, this species is here assigned to the genus Melchus , and the diagnosis of that genus revised such that the apex of the rostrum may be laterally compressed or cylindrical. Specimens (although very few) from different islands do not show any consistent differences warranting geographic recognition as distinct.

Natural history.— Label data indicates one specimen was collected from the bases of Euterpe globosa fronds on Dominica and two specimens were collected at uv lights on St. Lucia.

Derivation of specific name.—This species is named after my daughter Jessie Catherine Anderson. I’m sure her love of travelling will eventually take her to these diverse and interesting islands.

Figures

FIGURES 5 – 8. Melchus jessae. 5. Dorsal habitus, female. 6. Lateral habitus, female. 7. Rostrum, male. 8. Rostrum, female.