Melathra Franz

Franz, Nico M., 2011, Melathra Huyenae Franz, A New Genus And New Species Of Entimine Weevil (Coleoptera: Curculionidae: Entiminae) From Southwestern Hispaniola, The Coleopterists Bulletin 65 (4), pp. 352-362 : 353-359

Melathra Franz , new genus

( Figs. 1–14 )

Diagnosis. Melathra keys to Apotomoderes (“ Barynotini ”) in van Emden (1944), and variously to the naupactine genera assigned to couplets 117–122 in Anderson (2002; ∼ Artipus Sahlberg , Naupactus Dejean ) by virtue of the absence of a postocular lobe and vibrissae on the pronotum, the laterally positioned scrobe, the median sulcus on the rostrum, and the laterally positioned eyes. However, Melathra cannot be accommodated within any of the existing North American genera as circumscribed in Anderson (2002), and is indeed more closely related to the predominantly Hispaniolan geonemine genus Apotomoderes , sharing with the latter the following diagnostic features (Franz 2011): labial palps 2-segmented; transition of rostrum to head marked by a circum-capital suture; head with a postocular constriction; eyes laterally positioned on head; profemur with one pointed, cuticular tooth; metatibial apex simple (i.e., without an inner flange or an outer bevel); and aedeagus with groups of setae present in the dorsal subapical region. Nevertheless, Melathra is readily distinguished from Apotomoderes by the following traits (see also Franz 2010a): dorsal half of scrobe passing over eye (not entirely ventrad of eye as in Apotomoderes ); eyes in dorsal profile not "tilted" posteriad; pronotum not sexually dimorphic; profemoral tooth small, pointed, not knife-like (as in Apotomoderes ); protibia without an anteromesally positioned, ridge-like (and often toothed), cuticular projection; elytra with humeri obscure; wings partially “reduced” (not fully developed as in Apotomoderes ); female sternum VIII elliptical (not triangular); spermatheca with corpus swollen; and median lobe with strongly sclerotized flagellum and paired anterior, narrowly plicate sclerites (absent in Apotomoderes ). Melathra furthermore differs from Apotomoderes by the more uniformly dark brown scale coloration which is interrupted primarily by two anteromesally positioned, rusty brown spots on the elytra; a much less depressed post-epistomal region; a shorter and more foveate (less narrowly linear) median rostral sulcus; and the lack of a row of teeth along the ventral side of the metatibia in females. The aforementioned characteristics jointly serve to separate Melathra also from other as of yet undescribed Caribbean species of entimine weevils that were examined by the author, thereby justifying the erection of this new genus-level taxon.

Description. Female ( Figs. 1–3 ). Length 6.20– 9.97 mm, width 2.76–4.17 mm (n = 10); shape elongate-pyriform, length/width ratio 2.25–2.50; widest at midregion to posterior 1/3 of elytra. Integument dark (black), legs dark reddish brown. Small, subcircular, subcontiguous, appressed, variously colored scales densely arranged throughout body surface; scales (where not abraised) mostly pale white or grey-silver to tan or darker brown, somewhat translucent, yet characteristically light rusty brown (to orange) and metallic (visible at higher magnification) on lateral sides of pronotum, epipleura, and in anteromesal regions of elytra. Mouthparts: Mandibles ( Fig. 3 ) lacking scales, with 5–8 long, several shorter setae, mandibular scar positioned apicolaterally, slightly projected. Maxillae ( Fig. 7 ) with cardo elongate, basically widely bifurcate, lacking setae; stipes narrowly elongate, with lateral setae; galeo-lacinial complex mesally extending to apex of maxillary palpomere I, apically rounded, covered with short setae throughout, with several lacinial teeth (5–6 narrow and apical, wider and mesal; see Ting 1936), thereafter (along mesal margin) with tuft of long setae; palpiger with transverse row of setae; maxillary palps 3-segmented; I longer than II, with 2 apicolateral setae; II similar in length and wider than III, with multiple circumapical setae; III elongate, with parallel sulci, apically papillate. Labium ( Fig. 8 ) with prementum entirely covering maxillary palps; escudate-pentagonal; apical margin medially projected; each apicolateral region with 3–4 long setae; labial palps 2-segmented, not reaching apical margin of prementum; I and II similar in length, subquadrate; I with 1 apicolateral seta; II apically papillate. Rostrum: Length 0.96–1.46 mm, rostral/ pronotal length ratio 0.54–0.62, rostral length/width ratio 0.93–1.04. Dorsal outline of rostrum subquadrate; dorsolateral margins anteriorly diverging; apical margin triangularly incised. Nasal plate ( Vaurie 1963) weakly defined, slightly concaveinflected, posteriorly not carinate; epistoma forming inversely V-shaped, slightly angulate stripe between nasal plate and basal 3/4 of rostrum. Dorsal surface of rostrum slightly convex, with median, posteriorly narrowing sulcus extending (maximally) to imaginary midpoint between anterior margins of eyes, often shorter. Rostrum in lateral view nearly straight, anteriorly slightly expanded; occipital sutures welldefined, extending to ventral midpoint of rostrum. Ventral surface of rostrum with gular sutures fused (Lyal 1995), anteriorly terminating in large, deep fovea, thereafter hypostomal-labial sutures widely bifurcating, curved, not reaching labial prementum. Antennal insertion near anterior 1/5 of rostrum. Scrobe lateral, strongly curved and posteriorly widened, terminating anteriorly and directed ventrad of eye, though dorsal half passing over eye; anterior 1/2 of ventral margin of scrobe wide, convex, set off from lateral surface of rostrum by deep sulcus. Antennae 11-segmented; scape moderately stout; funicular antennomeres progressing from elongate to equilateral, clavate; club similar in length to funicular antennomeres III–VI; otherwise similar to Apotomoderes (see Franz 2010a). Head: Eyes laterally positioned, more or less evenly globular and protruded; separated (in dorsal view) by distance more than anterior-to-posterior length of each eye. Head with apparent postocular constriction extending along entire circumference, rostrum and head in lateral view angulate. Thorax: Pronotum equilateral, length/width ratio 0.92–0.96, pronotal/ elytra length ratio 0.34–0.36, slightly convex and globular; widest near midpoint; surface punctate, punctures homogeneously spaced; median sulcus absent. Anterolateral margins of pronotum slightly projected, postocular lobe and vibrissae absent. Scutellum exposed, semi-circular, covered with scales. Epipleura with mesepisternum triangular; mesepimeron dorsally obliquely narrowed; metepisternum linear, anteriorly abruptly widened; metepimeron entirely covered by elytron. Prosternum longer than mesosternum; procoxal cavities positioned at midpoint, contiguous, prosternal process short, elevated. Mesosternum slightly shorter than metasternum; mesocoxal cavities separated by distance nearly half as long as width of each mesocoxal cavity. Metasternum with median sulcus present as large, transverse fovea positioned anteriorly of posterior margin; metacoxal cavities widely separated; otherwise similar to Apotomoderes (see Franz 2010a). Metendosternite with stalk wide; hemiducts wide, truncate; dorsal margin of sheath undulate; anterior tendons positioned near midpoint between median keel and base of furcal arms; furcal arms short, slender, diverging at 30–45° in relation to median keel. Legs: Prothoracic and metathoracic legs each longer than mesothoracic legs. Profemoral/pronotal length ratio 1.09–1.19; profemur with 1 small, pointed (though not knife-like), cuticular tooth inserted at apical 2/5 on anteromesal margin. Protibial/ profemoral length ratio 0.92–1.00; protibia nearly straight, width similar throughout; anteromesal margin with row of 8–10 small, apically obliquely truncate cuticular teeth, each tooth distally with brownish, spiniform seta; protibial apex with anterior margin truncate, setal comb absent; mucro similar in length to tarsal claw. Protarsus with tarsomere I nearly 2X as long as II, elongate, clavate; II and III similar in length, equilateral to transverse, jointly similar in length to V; claws paired, separate, simple. Meso- and metafemora unarmed; mesotibia with anteromesal row of teeth more widely spaced, metatibiae with teeth not well-developed (obscure); metatibial apex simple, mucro absent, lateral margins each with a comb of spiniform setae of increasing length, yet without a bevel or flange (“corbel open”; Thompson 1992), surface surrounding metatarsal condyle glabrous. Elytra: Length/width ratio 1.77–1.81; widest near midregion; anterior margins jointly slightly wider than posterior margin of pronotum, nearly straight; humeri obscure, rounded; lateral margins subparallel along anterior 3/4, thereafter roundly converging, posteriorly attenuate. Elytra in lateral view plane to slightly convex; posterior declivity apparent though not strongly angulate, nearly straight. Elytra with striae I-IX complete, stria X incomplete and apparent only along marginal anterior 1/4; striae similar in width to intervals; punctures separated by distance similar to width of each puncture; intervals not elevated; with a tuft of aurate, linear, suberect scales at mesal margins of declivity. Wings ( Fig. 9 ): Wings present but not fully developed, shorter and more linear in comparison to Apotomoderes (see Franz 2010a), distally obliquely narrowed, likely not functional, though most alar veins and sclerites well-defined (see Fig. 9 ). Abdomen: Venter with segments III and IV jointed, slightly convex and elevated, V-VII separate, the latter with linear and increasingly longer, suberect, aurate scales; VII with several small, shallow, irregularly shaped impressions, lateral margins posteriorly triangularly converging, posterior margin narrowly rounded. Tergum VII lacking strigulate regions. Pygidium (tergum VIII) entirely covered by elytra. Terminalia: Sternum VIII ( Fig. 10 ) with anterior 3/4 (spiculum ventrale) narrowly stylate; posterior 1/4 (lamina) elliptical, entire (arms jointed), lateral margins continuously rounded, posterior margin slightly emarginate, posterior 1/4 of lamina with increasingly longer setae. Coxites ( Fig. 11 ) similar in length to spiculum ventrale, weakly sclerotized, laterally with sparsely arranged setae; styli more strongly sclerotized, short, ovoid, posteriorly with 2–3 longer setae. Spermatheca ( Fig. 12 ) variously C-shaped; collum and ramus not projected and widely separated; corpus large, tumescent; cornu slightly longer than corpus, continuously curved and apically pointing in a direction perpendicular to “axis” of collum, apex acute.

Male ( Figs. 4–6 ). Overall similar to female,though body shape slightly more slender (not pyriform) and pronotum slightly more globular. Length 6.14– 10.03, width 2.49–4.37 (n = 10); length/width ratio 2.30–2.47; rostral length 0.92–1.52 mm; rostral/pronotal length ratio 0.50–0.55, rostral length/width ratio 0.92–0.96; pronotal length/ width ratio 0.91–0.96, pronotal/elytral length ratio 0.36–0.38; profemoral/pronotal length ratio 1.07– 1.22; protibial/profemoral ratio 0.89–0.95; metatibia slightly longer than in female, apically curved, otherwise similar to protibia, row of cuticular teeth and mucro present; elytral length/width ratio 1.73–1.82; elytral declivity rounded, not angulate, less pronounced than in female, mesally positioned tuft of scales absent; venter with segment VII short, posterior margin widely rounded to truncate. Terminalia: Sternum VIII similar to Apotomoderes (see Franz 2010a). Spiculum gastrale ( Fig. 13 ) longer than median lobe; stylus slightly curved; posteriorly bifurcate, furcal arms elongate-triangular, anteriorly weakly sclerotized, posteriorly diverging and more heavily sclerotized, apices finely acute. Tegmen ( Fig. 14 ) more than 1.5X length of median lobe; tegminal apodeme slender, slightly sinuate; basal piece posteriorly Y-shaped. Aedeagus ( Fig. 14 ) with median lobe (aedeagal pedon) length/width ratio 6.04–6.42; basiventral margin roundly emarginate; lateral margins subparallel, gradually roundly converging along posterior 1/6, apex narrowly rounded. Median lobe in lateral view slightly curved along anterior 3/5, thereafter outline straight to slightly undulate; width similar throughout, except for gradually narrowed posterior 1/6, along which dorsolateral margins (and to a lesser extent the dorsal mesal area) are densely covered with short, fine setae (see also Franz 2010a); apex triangularly narrowed, slightly deflected. Internal sac with variously plicate membranes, though lacking denticulate regions; with well-developed, long and anteriorly and posteriorly strongly sclerotized flagellum (see Wanat 2007; a membranous flagellum was observed in the majority of taxa studied in Franz 2011), anterior end of flagellum with knob-like expansion, midregion not sclerotized, yet posteriorly (along region of ostium) connected to 2 narrowly elongate, subparallel, undulating, plicate sclerites which terminate in plicate “head” region that is acutely narrowed and recurved by 180°; ostium large, elliptical, lateral margins invaginated. Aedeagal apodemes nearly 3/5 as long as median lobe, sclerotized, slender.

Type Species. Melathra huyenae Franz.

Etymology. The genus name Melathra is a combination of the Ancient Greek words melas and lathra (see Brown 1956). The former signifies “black, dark” and refers to the dark habitus of the weevils, whereas the latter signifies “secretly, stealthy” and refers to the “mysterious character” of the genus, both taxonomically and in terms of life habits. The gender is feminine.

Figures

Figs. 1–3. Habitus of Melathra huyenae, female. 1) Dorsal; 2) Lateral; 3) Ventral.

Figs. 4–6. Habitus of Melathra huyenae, male. 4) Lateral; (5) Head, dorsal view; (6) Head, lateral view.

Figs. 7–9. Mouthparts and wings of Melathra huyenae. 7) Right maxilla, ventral view; 8) Labial prementum, lateral view; 9) Right hind wing. Not illustrated to scale.

Figs. 10–12. Female terminalia of Melathra huyenae. 10) Sternum VIII; 11) Coxites and styli; 12) Spermatheca. Not illustrated to scale.

Figs. 13–14. Male terminalia of Melathra huyenae. 13) Spiculum gastrale; (14) Tegmen and aedeagus, ventral and lateral views. Not illustrated to scale.