Chalepus walshii (Crotch, 1873)

Eiseman, Charles S., 2015, Notes on Leaf-Mining Chrysomelidae (Coleoptera) in New England, The Coleopterists Bulletin 69 (3), pp. 453-458 : 453-455

Chalepus walshii (Crotch, 1873)

At Harriman Point in Brooklin, Maine (44.290653° N, 68.532603° W) on 26 August, I found adults of this species feeding on foliage of Calamagrostis canadensis (Michx.) and Elymus virginicus L. (both Poaceae ) at the back margin of a salt marsh. In the immediate vicinity, I was able to find mines on both hosts, all of which were already abandoned except for one on C. canadensis , from which an adult emerged by 8 September. The following observations are based on examination of six mines on C. canadensis and three on E. virginicus .

The eggs and their coverings resemble those of C. bicolor but are attached to the upper leaf surface ( Fig. 2 ). On C. canadensis , one leaf had two eggs and one had three, but in both cases evidently just one larva survived, as there was a single pupal skin in each mine. Placement of the eggs ranged 9–70 mm from the leaf tip (average 39 mm), and when multiple eggs were present they were separated by 8–12 mm. On C. canadensis , the mine occupied the full width of the leaf for 17.5–23.0 cm from the tip, then extended another 0–1.5 cm along one side of the midrib (total length = 18.0– 24.5 cm). The mines in E. virginicus were somewhat shorter, occupying the full leaf width for 13.5–16.2 cm from the tip, plus an additional 0.5–3.0 cm along one side of the midrib (total = 16.5–17.0 cm).

The mines were full-depth and puffy, containing little or no frass. Presumably, the frass was expelled from the mines as I observed for C. bicolor ( Eiseman 2014) , but I did not see any adhering to the leaf margins. The adult emerges through a longitudinal split in the leaf rather than through a chewed exit hole. Without the pupal exuviae inside or the egg remains on the surface, the abandoned mines would be difficult to recognize as such.

Figures

Figs. 1–8. 1) Egg of Chalepus bicolor, lateral view); 2) Egg of Chalepus walshii, dorsal view; 3) Larva and leaf mine of Microrhopala xerene; 4) Abandoned mine of M. xerene, with pupal blister torn open; 5) Mine of Sumitrosis inaequalis in Symphyotrichum cordifolium; 6) Mine of Dibolia chelones, showing two frass types; 7) Mature larva of D. chelones; 8) Five young larvae of D. chelones in a single leaf.