Trigonorhinus limbatus (Say)

Janicki, Julia & Young, Daniel K., 2017, Nemonychidae and Anthribidae of Wisconsin (Coleoptera: Curculionoidea), Insecta Mundi 2017 (579), pp. 1-36 : 19-20

Trigonorhinus limbatus (Say)

(Fig. 27–28)

Anthribus limbatus Say 1826: 250 .

Brachytarsus plumbeus Leconte 1876: 406 .

Brachytarsus vestitus Leconte 1876: 406 .

Brachytarsus naviculus Jordan 1907: 379 .

Brachytarsus limbatus (Say) ; Blatchley and Leng 1916: 40.

Brachytarsoides limbatus (Say) ; Pierce 1930: 30.

Brachytarsoides rufodorsalis Dethlefsen 1954: 58 .

Brachytarsoides minor Dethlefsen 1954: 58 .

Brachytarsoides quadratus Dethlefsen 1954: 59 .

Brachytarsoides quadratus ssp. nigrinus Dethlefsen 1954: 60 .

Trigonorhinus limbatus (Say) ; Valentine 1957: 9.

Description. Length 1.8–3.2mm (head excluded). Integument black to dark reddish-brown, legs light reddish-brown. Vestiture consisting of white to light brown setae; pronotal setae pale grey or brown, in spots or intermixed with darker brown; elytral discal setae white, white and light brown intermixed, or entirely light brown, with light brown setae often in small, scattered spots. Rostrum moderately prolonged, narrowed apically, medial 1/3 prolonged apically; surface finely punctate. Frons weakly convex, weakly transversely impressed below eye level, surface finely punctate. Pronotal width 1.2X length, widest at basal angles; sides distinctly arcuate, strongly converging to narrowly rounded apical margin; disc evenly and strongly convex, weakly and transversely impressed before transverse carina, transverse carina basal, very weakly arcuate, acutely elevated; surface shining, with shallow, sparse punctures, interpunctural space punctulate or minutely reticulate. Elytral length 1.2X width, sides evenly and weakly arcuate to broadly rounded apex; disc evenly convex; striae weakly and narrowly impressed, with small, deeply impressed punctures; interstriae 3.0–4.0X strial width, minutely reticulate-granulate.

Diagnosis. Trigonorhinus limbatus can be distinguished from other Trigonorhinus species by its diffuse color pattern consisting of white to light brown setae, and by the pronotum possessing a shallowly emarginate base that is arcuate opposite the scutellum.

Natural history. Adults breed in the heads and stems of various flowers in Asteraceae , especially in those of Helenium . Specifically, they have been recorded on sneeze weed, Helenium autumnale . According to Howden (1992), Valentine observed that adult females use the toothed ovipositor to simply push aside parts of a composite flower head, or they may oviposit in stems. A Wisconsin series was recorded “mating and perhaps feeding on flowers of Helenium autumnale ”.

Phenology. In Wisconsin, adults have been collected June – August.

Collecting methods. The 31 Wisconsin specimens examined during this study from five counties represent a NEW STATE RECORD. Most specimens were hand-collected from H. autumnale .