Synobius lobicollis Sharp, 1899

Halstead, David G. H., 2020, New and little known Coleoptera (Silvanidae: Silvaninae) from Central and South America, Insecta Mundi 2020 (842), pp. 1-37 : 4-6

Synobius lobicollis Sharp

( Fig. 9–17 )

Synobius lobicollis Sharp 1899: 558 (type examined).

Synobius trigonaphilus Nevermann (manuscript name, unpublished - see below)

Diagnosis. The most obvious character for separating this species from S. lobatus is that provided by the lobed anterior angle of the pronotum, which in S. lobicollis is larger in comparison with the rest of the pronotum. Other useful characters are also of a comparative nature. Generally, the overall appearance of the pronotum in S. lobicollis is less transverse and usually somewhat trapezoidal (as figured by Sharp (1899)) (compare Fig. 9–10 with 7–8), the latter tendency does not seem to be a characteristic of S. lobatus . The transverse depression on the head is more arcuate in S. lobicollis (at least in specimens seen). The male genitalia of S. lobicollis and S. lobatus are very similar but the median strut and tegminal struts in specimens examined provide what appear to be good characters for distinguishing the species. Synobius lobicollis ( Fig. 14 ) has the median strut broadly expanded at the apex then narrowed to the basal bifurcation where it is one sixth of the apical breadth and its tegminal struts terminate in a narrow apex, whereas S. lobatus has the median strut very broadly expanded and almost semicircular at the apex then strongly narrowed to the basal bifurcation where it is one thirteenth of the apical breadth, its tegminal struts terminate in a broad rounded apex. Some additional comparisons are made in the following description.

Description. This description is based on 8 specimens, as listed below, and the measurements on 6 of them. Length of body, 4.50–4.81 mm; length to breadth ratio (breadth, maximum across elytra) 28.1–30.1:10.0; color and pubescence as in S. lobatus .

Head. Breadth (across eyes) to length ratio, 13.8–15.7:10.0; overall form, including puncturation and pubescence, similar to S. lobatus ; depression across median half of area between frons and vertex obviously arcuate; clypeal region somewhat convex; temples absent; eyes small, separated dorsally by 6.8–9.3× width of eye in dorsal view, slightly less widely spaced than in S. lobatus ; antennae, length to body length ratio, 10.0:40.2–45.2, closely similar to those of S. lobatus .

Pronotum. Medial breadth to mid-line length ratio, 10.5–11.2:10.0, not conspicuously transverse (appearing slightly elongate) mostly trapezoidal becoming slightly narrower anteriorly ( Fig. 9–11 ), obviously more depressed than elytra; margins with narrow rim; anterior angles forming prominent lobes; disc with shallow lateral depressions on each side of disc running into slightly deeper transverse depression situated towards base

Elytra. Length to greatest breadth ratio, 17.0–18.4:10.0, pubescence and other characteristics similar to those of S. lobatus .

Male genitalia ( Fig. 14–17 ). Parameres long, slightly less than 6× as long as broad, apical part of outer margin including outer part of apex, bearing 10–11 long setae (a few appeared spatulate on one paramere of the genitalia illustrated), inner half of apex with a few slightly shorter broader setae, inner margin with a few much smaller fine setae ( Fig. 15 ); median lobe longer than broad, apex broad, sides shallowly emarginate; median strut broadly expanded at apex then narrowed to basal bifurcation where one sixth of breadth across apex; tegminal struts narrowed to apical junction; 10–12 rods on each side towards ostium; sternites 8 and 9 ( Fig. 17 ), 8 with caudal margins straight, mainly short setae along them, at corners a few long setae (5 and 4 specimens examined), 9 with very short fine setae, as illustrated.

Material examined. Holotype (sex indet.) “ Synobius lobicollis Type D. S. Bugaba [handwritten by Sharp] / Type [circular, red-bordered label] / Sp. figured [printed] / Bugaba Panama Champion [printed] / B.C.A., Col. II, I” ( NHML).

Other material. (7 total) 4 specimens labelled by Nevermann ‘ Synobius trigonaphilus new species m’ [manuscript name, unpublished] as follows (* No habitat labels, only locality and determination labels on these specimens): 1 male, mounted on a card point with male sign on point and genitalia mounted on a separate card point beneath “ COSTA RICA F. NEVERMANN [printed] 28. viii. 36 [green label] / HAMBURG FARM REVENTAZON EBENE LIMON [green label, printed] / im nest von Trigona [handwritten] / TYPE [red label, printed] / Synobius trigonaphilus new species m. det. Nevermann 1936 [manuscript name, unpublished] / USNM 2045653” ( USNM) ; 1 male * with same data labels as above and male sign on card point but not dissected, also with “apparently nom. nudum REB 1940” ( USNM) ; 1 male * with same data as above and male sign on card point, also on a protective card beneath point “94d” ( USNM) ; 1 female * with same data labels, female sign on card point, also an additional card point bearing a specimen of Trigona (USNM) . 1 female “ COSTA RICA F. NEVERMANN 28. viii. 36 [green label printed except date] / Cotype [red label] / Synobius trigonaphilus new species m. det. Nevermann 1936 [manuscript name, unpublished] / Mus Zool Polonicum Warsawa 12 / 45” ( MIZP). 1 female and 1 male, mounted on the same card, male dissected, genitalia mounted on the same card by the author ( NHML, with data labels as for MIZP specimen, plus circular yellow-bordered Co-type label and “ Brit Mus 1937-365”, accession label) .

Figures

Figures 7–10. Synobius spp. pronota. 7–8) S. lobatus (Grouvelle). 7) Male, 8) Female. 9–10) S. lobicollis Sharp, both male. Scale line = 2.0 mm.

Figures 11–17. Synobius lobicollis Sharp, male. 11) Habitus. 12) Head, anterior lateral region showing antennal base and eye. 13) Antenna, enlarged. 14–17) Genitalia and associated sternites. 14) Genitalia, without internal sac. 15) Paramere, enlargement of apical half. 16) Internal sac, apical third. 17) Sternites 8 and 9. Scale lines for Figure 11 = 2.0 mm, for Figures 14 and 16–17 = 0.5 mm.