Eugnamptus angustatus (Herbst)

Young, Julia Janicki Daniel K., 2021, Survey of the Attelabidae of Wisconsin (Coleoptera: Curculionoidea), Insecta Mundi 2021 (891), pp. 1-61 : 11-12

Eugnamptus angustatus (Herbst)

( Fig. 9–12 )

Diagnosis. Eugnamptus angustatus exhibits great color variation, which has caused early taxonomic confusion and resulted in the description of a number of synonyms ( Hamilton 1990). Four different morphs exist within this species; the color variation can be recognized as: the typical form (42%) ( Fig.9–12 ), the dark-colored form (33%, only females), the pale-legged-color form (20%) and the red-headed-color form (5%). Pierce (1913) proposed these various morphs to be different species, however they are now recognized as synonyms. Eugnamptus angustatus can be recognized by the elytral integument that is always dark, by the punctures of the interstriae that are much smaller than those of the striae, and by the head with small and widely spaced setigerous punctures.

Description. Length 2.5–4.4mm (head excluded). Integument reddish brown to black; pronotum sometimes light red or reddish brown; legs light brown or reddish; elytra always dark. Head convex at upper level of eyes; surface with very small, weakly impressed, widely separated punctures. Rostrum arcuate, in male shorter than pronotum, in female as long as pronotum; sides in dorsal view parallel from eyes to antennal insertion. Pronotum length 1.1× width, widest at middle, moderately arcuate laterally, converging to truncate apex; disc with fairly large, shallow, round punctures, interpuncture space smooth, shining. Elytra length 1.8× width, width about 2.0× pronotal width; striae distinct, not impressed, with round, moderate, impressed punctures; interstriae much wider than striae, flat; strial and interstrial punctures each with 1 long, erect seta.

Natural history. This species is often collected from oak ( Quercus Linnaeus spp. ) and is known to mine dead oak leaves. They have also been recorded on walnut ( Juglans Linnaeus spp. ), dogwood ( Cornus Linnaeus spp. ), hickory ( Carya Nuttall spp. ), sassafras (Sassafras Boehmer spp.), black gum ( Nyssa Linnaeus spp. ), and the common persimmon ( Diospyros virginiana Linnaeus ). Hamilton (1980) recorded the life history of this species in northern Ohio on sassafras (Sassafras albidum (Nuttall) Nees von Essenbeck). The adults emerge in late May to early June and mate on mature sassafras trees, feeding preferentially on young developing leaves. After mating, the females will relocate to the ground to oviposit in dead leaves from the previous fall leaf drop. Larvae develop within the leaf as full depth leaf miners and reach the 4 th instar in 3–4 months; once they mature, they leave the mines to pupate in the soil and overwinter. In the lab, females have been observed to oviposit in the leaves of oak ( Quercus spp. ) and sweetfern ( Comptonia peregrina (Linnaeus) Coulter ).

Phenology. In Wisconsin, adults have been collected from June to September.

Collecting methods. Thirty-one Wisconsin specimens were examined during this study from 11 new counties, totaling 13 county records, as noted below. Specimens were collected by sweeping forest understory, beating oak or other hardwood trees, in pan traps and Malaise traps, as well as hand collected from hazelnut ( Corylus Linnaeus spp. ) and on wilted oak ( Quercus spp. ).

Distribution. United States. AL, AR, CT, DC, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, MI, MN, MO, MS, NC, NE, NJ, NY, OH, OK, PA, RI, SC, SD, TN, TX, VA, VT, WI, WV. Canada. ON, SK.

Wisconsin county records. This species has previously been recorded from Monroe and Washburn counties ( O’Brien and Wibmer 1982; Hamilton 1990; Downie and Arnett 1996). Columbia, Dane, Grant, Lafayette, Pierce, Rock, Sauk, St. Croix, Vernon, Waukesha, Wood.

Figures

Figures 9–10. Eugnamptus angustatus (Herbst) (M). 9) Habitus, dorsal view. 10) Habitus, lateral view.

Figures 11–12. Eugnamptus angustatus (Herbst) (F). 11) Habitus, dorsal view. 12) Habitus, lateral view.