Eusphalerum torquatum

Eusphalerum torquatum (Marsham, 1802)

Silpha torquata Marsham, 1802.

Eusphalerum torquatum; Moore and Legner 1975: 191; Zanetti 1987: 133; Herman 2001: 463.

Material examined: (13 specimens). CANADA. Newfoundland 2 mm 2 ff Goulds 2.07.1985 leg. Morris (CNC); 2 mm 7 ff St. John’s 23.07.1949 leg. Brown (CNC).

Published records. St. Johns and Topsail in 1965 (...); Nova Scotia in 1983 (CNC) (Brown 1967; Klimaszewski et al. 2013).

Measurements. Head length: 0.24-0.29; head width: 0.51-0.68; pronotal length: 0.48-0.57; pronotal width: 0.68-0.83; elytral length: 0.94-1.09; elytral width: 0.88-1.05; length (clypeus to apex of elytra): 1.75-2.01; total length: 1.8-2.2.

Description. Habitus as in Fig. 18. Head, pronotum, and elytra yellowish, elytra somewhat paler, neck often darkened; abdomen blackish or dark brown, prosternum yellowish, metasternum blackish; legs, antennae, and mouthparts yellowish, antennae darkened from antennomere 6-8.

Head with prominent eyes, postocular carina present and well marked, temples short, strongly convergent caudad, medial margin of eyes without longitudinal wrinkles. Head flat, postantennal depressions very superficial and tentorial pits small. Between ocelli a small tubercle (vestigial ocellum?) is often present, as in some European specimens. Neck clearly separated from the head (Fig. 19). Punctation very superficial on strongly microsculptured, obsolete, ground. Antennae slightly elongate, antennomere 1 rather elongate, twice as long as wide, 2 ovoid elongate, 3 twice as long as wide, 4-7 longer than wide, 8-10 subquadrate, 11 twice as long as wide, rather ovoid, sharpened at apex.

Pronotum transverse (ratio width/length = 1.4 on average), anterior margin wider than posterior in male, as wide as posterior in female, strongly convex in male, less convex in female, with a median superficial furrow in anterior two thirds, widest just in front of middle, lateral margins rounded at middle, convergent caudad in straight line, posterior angles marked and scarcely obtuse. Punctation dense but very superficial, ground with strong isodiametric microsculpture; pubescence long, yellowish, decumbent, directed caudally on disk, towards midline in front of posterior margin, depressions near posterior angles superficial, extending in front of middle of lateral margin.

Elytra scarcely elongate (ratio length from scutellum to apex / combined width of elytra = 1.0), widened towards apex, apices truncate medially in male, prolonged in short lobes (Fig. 21) in female, punctation somewhat coarse, somewhat confluent on glossy ground, pubescence short but clearly visible, scarcely decumbent.

Abdomen dull, microsculture well visible, pubescence long, decumbent.

Tibiae straight in both sexes, tarsomere 5 of posterior tarsi slightly shorter than 1-4 together.

Aedeagus as in Fig. 20.

Accessory sclerites of female as in Fig 22, spermatheca as in Fig. 23.

Comparative notes. Eusphalerum torquatum is easily separable from the other species living in Canada by its color pattern, which recalls light populations of E. californicum. The long pubescence, dense superficial punctation of pronotum, and impressed line that separates head from neck are distinctive. The form of the elytral apex of the female is also characteristic. The presence of a third vestigial ocellus is also recorded in the European species of the robustum group as well as occasionally in other omaliinegroup taxa.

Distribution. North America: CANADA: Newfoundland and Labrador, Nova Scotia (Map 1). Palaearctic region: Iberian Peninsula, Great Britain, Central Europe, mostly in western regions, also reported from Japan (Zanetti 1987). Various forms and subspecies have been described from southern France and Spain, differentiated in color and form of elytra of the females, but their validity is doubtful (Zanetti 1987). The North American specimens belong to the typical form. Eusphalerum torquatum is very probably an adventive species in North America.

Natural history. The species is regularly found on broom flowers, mostly Sarothamnus (Fabaceae), in Europe. This plant was introduced in North America and it is now widely distributed in the Pacific states, where it is considered a destructive invasive species, but it is not present in Newfoundland. The host plant(s) in this region is not known. Captures of E. torquatum in July.