Compsus argyreus (Linnaeus) 1758

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 : 44-49

Compsus argyreus (Linnaeus) 1758 , p 384

( Figures 1 and 2 )

Description

Male. Length 6.07–7.72 mm, width 2.37–2.91 mm; shape slightly pyriform, length/ width ratio 2.56–2.65 (n = 2); greatest width near posterior third of elytra. Integument reddish brown to black; setae (narrow scales) sparsely and evenly arranged, recurvate, pale white; scales densely and evenly arranged, completely covering integument, subcircular, appressed, pearly white or light green metallic (iridescent); scales of each colour interspersed with characteristic though variable pattern; light green metallic scales arranged in wide longitudinal or diagonal lines, or in irregular though bilaterally symmetrical patches; green scales predominant on prothoracic legs and meso- and metatibiae.

Mouthparts. Mandibles with approximately eight setae adjacent to scar. Maxillae with cardo longitudinally twisted; stipes extending to mesal edge of palpiger, lateral margin with four to five setae of various lengths, mesal margin with two to three setae, centrally with finely lamellate region; galeo-lacinial complex extending to midpoint of maxillary palpomere I, apical quarter elevated, angulate, mesal margin with five to eight very long setae and two lacinial teeth, apical region densely setose (setae apically similar to lacinial teeth); palpiger apically with transverse row of longer setae; maxillary palps three-segmented; I nearly three times as long as II, apicolateral margin with two setae; II slightly shorter than III, with two setae positioned on apicolateral and apicomesal edges; III with several longitudinal sulci. Labium with prementum entirely covering maxillary palps; trapezoidal to escudate, apical margin arcuate to slightly irregular; ventrally with four to six evenly spaced long setae on each side, apicocentral region with sparse, short setae; labial palps three-segmented, III ending short of apical margin of prementum; I similar in length to II, apicolateral margin with one seta; II slightly shorter than III; III elongate.

Rostrum. Length 0.85–1.11 mm, rostrum/pronotum length ratio 0.56–0.6, rostrum length/width ratio 0.98–1.08; shape in cross-section subrectangular. Dorsal outline of rostrum subquadrate to trapezoidal, anteriorly widened; dorsolateral margins slightly arcuate, anteriorly diverging, elevated, posteriorly evenly convex; apical margin emarginate-triangular, moderately incised. Nasal plate (see Vaurie 1963) large, distinctly projected from anterior region of rostrum, posteriorly with a large, inversely V-shaped carina. Epistoma distinctly depressed, partially covered with scales. Dorsal surface of rostrum with one deep, median, anteriorly widened sulcus, extending from antennal insertion to midpoint between eyes; and with two shorter, anteriorly diverging, posteriorly widened, dorsolateral sulci; ventrolateral margins slightly arcuate, anteriorly diverging. Rostrum in lateral view apically gradually expanded; ventrolateral sulci present; scales ventrally predominantly pearly white, though light green metallic along apical margin; margins of mandibular incision with evenly spaced, suberect setae. Antennal insertion near anterior 2/5. Scrobe lateral, slightly arcuate, initiating in apicodorsal region, terminating in basilateral region, anteriad of eye, posteriorly covered with scales.

Antennae 12-segmented. Scape extending to region between posterior margin of eye and anterolateral margin of pronotum, and through ventral half of eye (in idealized position), covered with setae and scales. Funicle seven-segmented, slightly longer than scape; funicular antennomeres progressing from distinctly to slightly elongate, clavate; II similar in length to I; VII slightly longer than VI. Club with four distinct visible segments (terminal annulation fully differentiated), similar in length to funicular antennomeres IV–VI, nearly twice as long as wide, dark brown to black; I longer than II, III and IV each shorter.

Eyes subcircular, anterior margin nearly straight; eyes separated from anterolateral margin of pronotum by nearly 15 rows of scales, position dorsolateral, interocular distance slightly shorter than maximum width of eye; with nearly 20 facets along maximum diameter.

Head with short median stripe of light green-metallic scales along occiput; each mesal margin adjacent to eye with row of long, suberect setae

Thorax. Pronotum equilateral, length/width ratio 0.93–0.95, pronotum/elytra length ratio 0.34–0.35; greatest width near central region or at posterior margin; dorsal surface slightly convex, foveate to punctate; scales evenly appressed, with alternating, irregular stripes of pearly white and light green metallic scales (particularly in lateral region); with anteromesally directed, recurvate setae; median sulcus extending along entire pronotum. Anterodorsal margin of pronotum slightly shorter than posterodorsal margin; dorsolateral margins anteriorly converging, posteriorly subparallel; posterodorsal margin slightly bisinuate, medially projected, with densely arranged, plumose setae. Pronotum in lateral view subquadrate to tubular, slightly expanded above procoxal cavities; anterolateral margin slightly projected, without postocular lobe, with small region of scales projecting anteriorly along slightly arcuate region, postocular vibrissae absent. Metascutum partially covered with plumose scales. Scutellum pentagonal to subcircular, covered exclusively with scales.

Prosternum slightly longer than mesosternum, with one transverse sulcus on each side anteriorly and posteriorly of procoxal cavities; procoxal cavities contiguous. Mesosternum similar in length to metasternum, intercoxal process slightly elevated, with recurvate setae; mesocoxal cavities separated by distance nearly one quarter of the width of each mesocoxal cavity. Metasternum with median sulcus reduced to a shallow, transverse-triangular fovea near posterior margin; metacoxal cavities separated by distance nearly half as long as width of each mesocoxal cavity.

Metendosternite with stalk slightly longer than furcal arms, equilateral, lateral margins dorsally converging; anterior tendons inserted at mesal one-third between centre of lamina and furcal arms; furcal arms dorsally diverging.

Legs. Prothoracic legs slightly longer than mesothoracic legs; scales predominantly pearly white on femora yet with light green metallic regions near midpoint of lateral side, the latter scales predominant along mesal side and on tibiae; with evenly spaced rows of whitish, recurvate setae along femora and tibiae. Profemur/pronotum length ratio 1.24–1.30; profemur slightly sinuate, in cross-section subcircular; unarmed. Protibia/profemur length ratio 0.97–1.00; protibia slender, slightly arcuate, in cross-section subquadrate, apically expanded; ventral margin with row of 8–10 small cuticular teeth, each tooth on distal side with 1 aurate seta; protibial apex with anterior margin slightly arcuate; setal comb absent; mucro similar in length to tarsal claw, surpassed by patch of whitish setae. Protarsus with tarsomere I elongate; tarsomere II equilateral. Protarsal claw paired, separate, simple. Mesothoracic legs slightly shorter than metathoracic legs; mesofemur slightly longer than metafemur; mesotibia similar in length to metatibia. Metatibia straight; metatibial apex with anterior margin obliquely truncate, expanded, setal comb with setal length similar throughout; surface surrounding tarsal condyle covered with scales; both inner flange and outer bevel with a row of spines (“corbel enclosed”).

Elytra. Length/width ratio 1.84–1.88; greatest width near posterior third; anterior margins jointly similar in width to posterior margin of pronotum, projected along striae I–VI (corresponding to emargination of posterior margin of pronotum); humeri oblique, slightly projected; lateral margins slightly diverging along anterior two-thirds, gradually converging along posterior third; posterior margins narrowly arcuate. Elytra in lateral view with dorsal outline subplane to slightly convex; posterior declivity distinct, strongly angulate. Elytra with nine complete striae and one incomplete stria; striae similar in width to intervals; stria X indistinct along central third; punctures separated by distance slightly longer than width of each puncture; intervals convex, slightly elevated; setae similar in length to width of intervals, recurvate, arranged in evenly spaced rows along every other strial interval (I, III, V, etc.); scales covering entire integument, subcircular to spatulate; with characteristic, symmetrical, though individually variable pattern of pearly white scales interspersed with light green metallic scales arranged in three to four main, linear to irregular to semicircular to V-shaped patterns, patterns in some individuals interrupted and restricted to mesal and lateral margins and to smaller patches including only one to five strial punctures.

Wings fully developed, elongate, wing/body length ratio 1.09–1.16, wing length/ width ratio 3.55–3.57; anterior margin nearly straight; posterior margin slightly arcuate; anal lobe absent.

Abdomen. Venter with sterna III–VII superficially separate; III convex, elevated, posterior margin with mesal concavity facing posteriorly; suture separating III and IV deep, sinuate; IV centrally subplane, laterally slightly convex; V and VI jointly slightly shorter than IV; V–VII subplane, sutures slightly emarginate; IV–VI elevated, with posterior face, VII more retracted, subplane, posterior margin straight. Pygidium subcircular; posterior margin medially slightly emarginate, ventrally plicate.

Terminalia. Sternum VIII consisting of two triangular sclerites; posterior margin of each sclerite arcuate, with sparsely arranged short setae and one to two longer setae. Spiculum gastrale ( Figure 2B ) longer than median lobe; posteriorly bifurcate (Y-shaped), furcal arms triangular, explanate, margins slightly serrate, posteriorly diverging; posteriorly more strongly sclerotized, slightly angulate, triangularly narrowed; each arm densely porose in less strongly sclerotized anterior quarter, lacking setae. Tegmen nearly three-quarters the length of median lobe; basal piece with two narrowly triangular projections, each projection finely and densely denticulate, more so towards apex. Aedeagus ( Figure 2A ) with median lobe length/width ratio 4.18–4.3 (n = 2); anteroventral margin strongly emarginate; lateral margins subparallel along anterior two-thirds, slightly converging along posterior third; apex triangularly narrowed. Median lobe in lateral view arcuate, anterior half evenly deflexed, posterior half straight to slightly reflexed; width similar throughout anterior two-thirds, gradually narrowed along posterior third; apex explanate, very slightly reflexed. Internal sac with densely arranged nodulate projections, posteriorly (along ostium) with one complex sclerite consisting of two subparallel (adjacent), dorsoventrally oriented laminae, and one posterior sclerite with basal rami surrounding apical region of laminae, apical region narrowly incudate, with one dorsal and one ventral projection. Adeagal apodemes slightly shorter than median lobe, slender.

Female ( Figure 1A–F ). Length 9.24–9.57 mm, width 3.85–4.07 mm; length/width ratio 2.35–2.40 (n = 2); greatest width near posterior third of elytra. Rostrum length 1.31–1.35 mm, rostrum/pronotum length ratio 0.62, rostrum length/width ratio 0.96–0.98; rostrum in dorsal view subrectangular, apically less expanded. Eyes semi-circular, interocular distance nearly 1.5 times as long as maximum width of each eye. Pronotum length/width ratio 0.78–0.87; pronotum/elytra length ratio 0.31; greatest width near central region; dorsolateral margins anteriorly more strongly converging. Metasternum ventrally subplane, concave in posterior half, posteromedian region deepened into a distinct fovea. Protibia/profemur length ratio 0.93–1.00. Elytra length/width ratio 1.72–1.80; greatest width near central region to posterior 1/3 of elytra; posterior declivity distinct, strongly angulate, slightly emarginate; strial intervals more strongly elevated. Venter with sternum III centrally subplane, laterally slightly convex, strongly elevated, anterior margins slightly separated, laterally angulate; IV centrally slightly convex, laterally convex; VII triangular, lateral margins posteriorly strongly converging, posterior margin narrowly emarginate. Pygidium subtriangular, lateral margins posteriorly strongly converging, posterior margin truncate, shallowly and narrowly emarginate, ventrally not plicate.

Terminalia. Tergum VII with anterior margin medially with linear incision; with small posterior region covered with longer setae. Sternum VIII ( Figure 2C ) with anterior two-thirds stylate; posterior third triangular to spatulate, medially fused (not bifurcate), with narrow median canaliculus, each arm longitudinally slightly plicate, posteriorly with triangular to V-shaped region of longer setae. Coxites nearly 3/5 the length of the sternum VIII; styli short, posterolaterally with three to four setae. Genital chamber slightly shorter than sternum VIII. Spermatheca ( Figure 2D )?-shaped; ramus long and sclerotized, narrowly separated from slightly projected collum (corpus short); cornu (apical three-fifths) narrowly arcuate, apex acute, slightly deflected.

Variation

The examined material varies primarily in size and in the alternating patterns of white and light green metallic scales on the pronotum and elytra.

Specimens examined

“ Bolivia, S.C. [ Santa Cruz ], 10 mi. W. Portachuelo, April 11, 1978, at night, G.B. Marshall ” (one male, CWOB) ; “ Bolivia, S.C. [Santa Cruz], Pump Sta. Caranda, 20 mi. SW. Portachuelo , at night, March 22, 1978 / Collector: G.B. Marshall ” (one male, CWOB) ; “ Bolivia, Dpto. Beni, 2.5 km N. Rurrenabaque, 14°25′29″S, 67°30′40″W, 11 July 1998, K.B. Miller, colr.” (two females, NMFC) .

Figures

Figure 1. Habitus of Compsus argyreus, female. (A) Dorsal view; (B) lateral view; (C) ventral view; (D) head, dorsal view; (E) head, lateral view; (F) metatibia, lateral view.

Figure 2. Terminalia of Compsus argyreus. (A) Aedeagus, ventral and lateral view; (B) speculum gastrale, ventral view; (C) posterior region of female sternum VIII, ventral view; (D) spermatheca. Note: Shaded areas of the median lobe indicate characteristic membranous or lightly sclerotized regions.