Merhynchites bicolor (Fabricius)

Young, Julia Janicki Daniel K., 2021, Survey of the Attelabidae of Wisconsin (Coleoptera: Curculionoidea), Insecta Mundi 2021 (891), pp. 1-61 : 17-18

Merhynchites bicolor (Fabricius)

( Fig. 17–18 )

Diagnosis. Merhynchites bicolor can be distinguished by the red prothorax, elytra and base of head, and by the larger size. It is very similar to M. wickhami , the western rose curculio, which has a more western distribution and is not known from Wisconsin. Merhynchites bicolor can be recognized by the base of the head that is red as opposed to black, by the elytral strial punctures that are larger than the interstrial punctures, by the wider eyes (0.12–0.14 mm wide as opposed to 0.07–0.10 mm in M. wickhami ), by the straighter rostrum, by the smooth elytral interstriae, and by the spiculum gastrale with the lateral margin bearing an acute, tooth-like process, which is absent in M. wickhami .

Description. Length 4.5–5.5 mm (head excluded). Integument black; prothorax, elytra and base of head red or reddish brown to light yellow. Head dull or shining, base of head red, apex usually black; surface with elongate punctures between eyes, interpuncture space weakly elevated, carinate at base of rostrum. Rostrum straight (more so in female), distinctly punctured, with 1 weakly elevated, longitudinal median ridge; longitudinally impressed basally in front of eyes. Eyes strongly convex. Pronotal width 1.1× length, widest at middle; broadly arcuate laterally, strongly converging to broadly rounded apex; disc distinctly convex, with moderate, impressed punctures, interpuncture spaces moderately shining, smooth. Elytral length 1.3× width, width at base 1.5–1.6× pronotal width; striae with large punctures; interstriae 1.5–2.0× strial width, smooth, with fine, erect, scattered setae. Pygidium densely punctured. Sexual dimorphism present in rostrum and legs: prothoracic coxae of male with round to oval, densely setose pits apically.

Natural history. This species is commonly known as the rose curculio or the rose weevil as it is most often found on roses ( Rosa Linnaeus spp. ) as well as species of Rubus ; it can be an occasional pest of cultivated roses, blackberries, and raspberries. Larvae are recorded to develop in the hips of these plants and feed on the achenes. In Wisconsin, it has been reared from hips of Carolina rose ( Rosa carolina Linnaeus ), smooth rose ( Rosa blanda Aiton ) and wild prairie rose ( Rosa arkansana Porter ). It has also been found on rugosa rose ( Rosa rugosa Thunberg ).

There is much published on this species: Chittenden (1901) reported on pest species including M. bicolor that are found on ornamental plants; Cooley (1903) reported that M. bicolor is an insect pest; Lovett (1915) reported that M. bicolor injures blackberry buds; Robertson (1923) investigated M. bicolor in Manitoba and how it affected roses; Balduf (1959) reported on insects including M. bicolor that are associated with rose hips; finally, Hamilton and Kuritsky (1981) described the larva and pupa of M. bicolor .

Phenology. In Wisconsin, adults have been collected from April to August, with a peak in June and July.

Collecting methods. During this study, 239 Wisconsin specimens were examined from 27 counties, forming a total of 28 county records. This species is most commonly hand-collected from wild roses. It is also often collected by sweeping roses, sweeping fields where roses are present, or by rearing from hips of various rose species.

Distribution. United States. AB, AZ, CA, CO, CT, DC, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MO, MT, ND, NE, NH, NJ, NV, NY, OH, OR, PA, RI, SC, SD, UT, VA, WA, WI, WV, WY. Canada. BC, MB, NF, SK.

Wisconsin county records. This species was previously recorded from Barron, Crawford, and Kenosha counties ( O’Brien and Wibmer 1982, Downie and Arnett 1996). Ashland, Barron, Brown, Burnett, Crawford, Dane, Dodge, Douglas, Grant, Green, Iowa, Jackson, Jefferson, Kenosha, Manitowoc, Marathon, Marinette, Marquette, Milwaukee, Monroe, Polk, Portage, Racine, Richland, Sauk, St. Croix, Waukesha, Waushara, Winnebago, Wood.

Figures

Figures 17–18. Merhynchites bicolor (Fabricius). 17) Habitus, dorsal view. 189) Habitus, lateral view.