Lachnopus valgus (Fabricius) 1775

Franz, Nico M., 2010, Redescriptions of critical type species in the Eustylini Lacordaire (Coleoptera: Curculionidae: Entiminae), Journal of Natural History 44 (1 - 2), pp. 41-80 : 72-77

Lachnopus valgus (Fabricius) 1775 , p 150

( Figures 16–18 )

Description

Male ( Figure 16A–F ). Length 7.46–10.56 mm, width 3.3–4.85 mm; shape oval to elongate, length/width ratio 2.18–2.26 (n = 4); greatest width at humeri or near anterior one-third of elytra. Integument light reddish brown (teneral specimens) to dark reddish-brown; setae present mainly on tibiae and tarsi, appressed to recurvate, argentate or aurate, setae along ventral margin of metatibia strongly modified; scales sparsely arranged, partially or entirely exposing integument, oval (width similar throughout), pearly white (iridescent); scales sparsely arranged on dorsal side, resulting in large glabrous regions, yet also with variously localized areas of higher scale concentration (subcontiguous), scales laterally and ventrally more densely arranged, contiguous in some regions.

Mouthparts. Mandibles with approximately five setae adjacent to scar. Maxillae ( Figure 17B ) with cardo sinuate, apically strongly oblique; stipes slightly arcuate, width similar throughout, lateral margin with two to four setae; galeo-lacinial complex extending to apex of palpomere II, mesal margin with four lacinial teeth; maxillary palpomere I nearly 1.5 times as long as II; II similar in length to III. Labium ( Figure 17B ) with prementum trapezoidal to pentagonal, apical margin angulate, medially projected; each apicolateral region with one setae on dorsal surface and two setae on ventral surface; labial palpomeres II and II protruding from apical margin of prementum; I slightly longer than II.

Rostrum. Length 1.15–1.60 mm, rostrum/pronotum length ratio 0.72–0.76, rostrum length/width ratio 1.26–1.60. Dorsal outline of rostrum rectangular; dorsolateral margins apically slightly converging, slightly arcuate, constricted near antennal insertion, evenly convex. Nasal plate very small (obscure), level with anterior region of rostrum, posteriorly with a weak convex semi-circular elevation. Epistoma slightly depressed, posteriorly with several appressed setae. Dorsal surface of rostrum subplane, with sparsely arranged scales and setae, median line rugulose, with intercalating carinulae, apically triangularly expanded, terminating on each side in three to four aurate setae, dorsolateral sulci absent; ventrolateral margins straight, anteriorly diverging. Rostrum in lateral view with width similar throughout; ventrolateral sulci restricted to basal third of rostrum. Antennal insertion near anterior quarter. Scrobe glabrous.

Antennae with scape extending to posterior margin of eye, and through region ventrad of eye (in idealized position), covered exclusively with setae. Funicle distinctly longer than scape, very slender; funicular antennomere II slightly shorter than I. Club similar in length to funicular antennomeres III–VI, nearly four times longer than width, reddish brown; I and II similar in length, III and IV each slightly shorter.

Eyes elliptical, oriented horizontally, posterior margin nearly straight; eyes separated from anterolateral margin of pronotum by minimally 3 rows of scales; with nearly 20 facets along maximum diameter.

Head with frons and occiput in lateral profile slightly angulate, ventrolaterally with sparsely arranged, pearly white scales.

Thorax. Pronotum trapezoidal, length/width ratio 0.62–0.69, pronotum/elytra length ratio 0.27–0.29; greatest width at posterior margin; dorsal surface glabrous to punctulate, with one row of evenly spaced shallow punctures along anterior and anterolateral margins, and with sparsely arranged and variously oriented scales; median sulcus absent. Anterodorsal margin nearly half as long as posterodorsal margin; dorsolateral margins posteriorly gradually diverging; posterolateral edges present; posterodorsal margin slightly arcuate. Pronotum in lateral view conical, surface punctulate; anterolateral margin with one row of short setae along margin ventral half. Metascutum glabrous. Scutellum semi-circular, glabrous.

Prosternum similar in length to mesosternum, anterior margin with row of anteriorly directed scales, posterior intercoxal projection strongly elevated. Mesosternum with mesocoxal cavities narrowly separated by distance nearly one-sixth of the width of each mesocoxal cavity. Metasternum with median sulcus forming a large posterior fovea, and with sparsely arranged setae; metacoxal cavities separated by distance similar to width of each metacoxal cavity.

Metendosternite with stalk longer than furcal arms; anterior tendons inserted near base of furcal arms.

Legs. Prothoracic legs with sparsely arranged, linear scales. Profemur/pronotum length ratio 1.44–1.54; profemur straight, in cross-section elliptical. Protibia/profemur length ratio 1.03–1.05; protibia in cross-section elliptical; ventral margin with evenly spaced rows of aurate setae, and with row of 10–15 cuticular teeth; protibial apex with mucro surpassed by 2–3 groups of reddish brown setae. Protarsus with tarsomeres I and II equilateral. Mesothoracic legs distinctly shorter than metathoracic legs. Metathoracic legs with metacoxa triangular, margins posteriorly converging at nearly 90°; metafemur with densely arranged noduli throughout (slightly concave) posterior side, noduli particularly prominent and dense along carinate posterodorsal edge, partially extending to ventral surface; metatibia with basal quarter straight, width gradually expanding, apical three-quarters (strongly) arcuate, rows of teeth or spine-like setae absent, yet anteroventral margin with one very large, triangular, apically truncate tooth inserted at basal quarter, thereafter (distally) ventral surface subplane, with multiple densely arranged rows of long, aurate setae, and with densely arranged noduli throughout entire ventral surface, and particularly along posteroventral edge; metatibial apex with setae dorsally short, length increasing towards condyle; surface surrounding tarsal condyle glabrous.

Elytra. Length/width ratio 1.63–1.68; greatest width at humeri or near anterior third; anterior margins jointly slightly wider than posterior margin of pronotum, not projected; lateral margins subparallel along anterior two-thirds, gradually arcuately converging along posterior third. Elytra in lateral view with dorsal outline evenly convex; posterior declivity obscure, only slightly angulate. Elytra with 10 complete elytral striae; stria X complete and converging with stria IX near midpoint where 4–8 punctures are immediately adjacent to each other; punctures separated by distance slightly shorter than width of each puncture, each puncture with 1 spatulate scale; strial intervals slightly convex; setae absent; scales exposing integument, arranged in irregular, moderately dense patches, or very sparse to almost entirely absent.

Wings with wing/body length relation 1.34–1.43, wing length/width ratio 2.92–2.96; anterior margin slightly sinuate; posterior margin nearly straight.

Abdomen. Ventral sterna III and IV connected, V–VII separate; III and IV elevated (IV with posterior face), centrally subplane, laterally slightly convex, anterior margin of III arcuate, mesally strongly projected; suture separating III and IV mesally shallow, laterally deeper; posterior margin of VII arcuate. Pygidium trapezoidal; posterior margin slightly arcuate, ventrally deeply and widely emarginate.

Terminalia. Sternum VIII consisting of two trapezoidal sclerites; posterior margin of each sclerite triangular, with three to five setae. Spiculum gastrale ( Figure 18B ) slightly longer than median lobe; posteriorly bifurcate (Y-shaped), furcal arms elongate, slightly arcuate, posteriorly diverging, mesal margins with one triangular projection. Tegmen similar in length to median lobe. Aedeagus ( Figure 18A ) with median lobe length/width ratio 5.63–5.65 (n = 2); lateral margins subparallel to slightly emarginate, greatest width anteriorly; apex widely truncate, apical margin slightly emarginate. Median lobe in lateral view evenly deflexed; width gradually narrowed towards apex; apex explanate, reflexed. Internal sac basally with two small, uncinate sclerites, apical region with two contiguous, rectangular to triangular, explanate sclerites, each sclerite apically slightly narrowed, overlapping, lateral margins slightly undulate.

Female. Length 9.31–10.96 mm, width 3.93–4.80 mm; length/width ratio 2.28–2.37 (n = 4); greatest width at humeri to near central region of elytra. Rostrum length 1.15–1.38 mm, rostrum/pronotum length ratio 0.60–0.61, rostrum length/width ratio 1.26–1.33; posterior margin of epistoma mesally with one small fovea. Pronotum length/width ratio 0.62–0.65; pronotum/elytra length ratio 0.26; greatest width at posterior margin; dorsolateral margins anteriorly more strongly converging, anterodorsal margin slightly emarginate. Metasternum ventrally subplane, concave in posterior half, posteromedian region deepened into a distinct fovea. Protibia/profemur length ratio 0.97–1.00. Metatibia similar to protibia, lacking large ventral tooth and other modifications present in male. Elytra length/width ratio 1.81–1.83; posterior declivity indistinct, elytra posteriorly evenly convex. Venter with sterna III and IV centrally subplane, laterally slightly convex; VII triangular, posterior margin narrowly arcuate. Pygidium trapezoidal, posterior margin narrowly arcuate, not emarginate.

Terminalia. Tergum VII longitudinally plicate; surface covered with short setae, each posterolateral region with longitudinal section of densely arranged, short, stridulatory setae; posteriorly with longer setae. Sternum VIII ( Figure 18C ) with anterior three-fifths stylate; posterior two-fifths pentagonal, spatulate, medially fused (not bifurcate); otherwise as in C. argyreus . Spermatheca ( Figure 18D ) falcate (sickle-shaped); ramus and collum contiguous, relatively short, similarly oriented; corpus short, globular, with small projection at inner side; cornu (apical half) narrowly arcuate, apex digitate.

Variation

The examined specimens vary considerably in size, integument colour (light brown in teneral specimens to nearly back in fully pigmented specimens), and the presence and density of scales throughout the body. The length and curvature of the male hind

tibia may exhibit positive allometry, as these modified structures appear to function in fights among males ( Franz 2003).

Specimens examined

“ St. John, Road 10 East, 24-I-1986, N. Virkki, yellow legume” (two males and two females, CWOB); “Anna’s Hope, St. Croix, V.I. [ U.S. Virgin Islands], May-1942, O. García ” (two males and two females, UPRM) .

Figures

Figure 16. Habitus of Lachnopus valgus, male. (A) Dorsal view; (B) lateral view; (C) ventral view; (D) head, dorsal view; (E) head, lateral view; (F) metatibia, lateral view.

Figure 17. Mouthparts of Lachnopus valgus. (A) Right maxilla, ventral view; (B) labial prementum, ventral view.

Figure 18. Terminalia of Lachnopus valgus. (A) Aedeagus, ventral and lateral view; (B) spiculum gastrale, ventral view; (C) posterior region of female sternum VIII, ventral view; (D) spermatheca.