Dibolia chelones Parry, 1974

Eiseman, Charles S., 2015, Notes on Leaf-Mining Chrysomelidae (Coleoptera) in New England, The Coleopterists Bulletin 69 (3), pp. 453-458 : 456

Dibolia chelones Parry, 1974

Previously ( Eiseman 2014), I discussed abandoned leaf mines on Chelone glabra L. ( Plantaginaceae ) that I attributed to this species. On 3 July in Granville, Massachusetts (42.098817° N, 72.886339° W), I found a single yellow-orange larva in a similar mine. This was apparently a secondary mine, since I was unable to find the egg. For the first 32 mm of this full-depth, linear mine, the frass was very fine and squiggly as previously described, but for the remain- der of the mine it was mostly concentrated in a central line which appeared frizzy under magnification ( Fig. 6 ). After mining a total of 150 mm in the 6-cm leaf, the larva moved to a new leaf. Here, it mined for 12 mm, emerged at the leaf tip, and then mined for another 35 mm at the base of the same leaf. It finished feeding on 6 July, at which point it was 4 mm long ( Fig. 7 ), and burrowed down within an hour of being placed in a jar of soil. The adult emerged by 22 July.

I reared adults from leaf mines collected at three other locations in Massachusetts in the summer of 2014. Larvae collected in Worthington (42.379977° N, 72.929313° W) on 7 July began burrowing on 9 July, and adults emerged beginning on 30 July. On 16 July, a single parasitoid, Pnigalio flavipes (Ashmead) (Eulophidae) , emerged from one of these mines. Young larvae collected in Northfield (42.647090° N, 72.428234° W) on 15 July emerged as adults during 3–6 August. Finally, I collected nine larvae in Pittsfield (42.445844° N, 73.198090° W) on 15 August, and five of them exited on the same day. Seven adults emerged on 2 September and the remaining two on 3 September. Having worked throughout July–September in wet- lands where C. glabra was present, it is my impression that D. chelones is univoltine, and the Pittsfield larvae simply had an unusually late start.

In one leaf, I located two oval eggs embedded in the upper leaf surface at the beginnings of mines; one was 0.7 mm by 0.3 mm and the other 0.8 mm by 0.4 mm. As I have observed in Dibolia borealis Chevrolat on Plantago major L. ( Plantaginaceae ), the young larvae are pale whitish (appearing greenish inside the leaf) rather than yellow-orange. I found up to six D. chelones larvae mining in a single leaf ( Fig. 8 ). In general, it appears that younger larvae produce squiggly frass and older larvae leave a compact central frass line. Mines are often highly contorted and confined by the midrib (except at the very tip of the leaf), the leaf margin, and feeding holes made by adults, which are irregular in shape and typically no more than 3 mm across.

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.