Chalepus bicolor (Olivier)

Eiseman, Charles S., 2014, New Host Records and Other Notes on North American Leaf-Mining Chrysomelidae (Coleoptera), The Coleopterists Bulletin 68 (3), pp. 351-359 : 353

Chalepus bicolor (Olivier)

This beetle has long been known to be a leafminer in various species of Dichanthelium (Hitchc. and Chase) Gould (Poaceae) ( Clark et al. 2004), but I have found no specific information about the larval habits. On 2 July 2013 in Pelham, Massachusetts, I found a larva in a small blotch mine at the edge of a leaf of Dichanthelium clandestinum (L.) Gould. The mine was full-depth (with all of the mesophyll consumed) and was completely free of frass. Small coils of dark, stringy excrement projected from the leaf edge at regular intervals ( Fig. 4 ). Although the larvae of several groups of leaf-mining Lepidoptera are known to expel excrement from their mines (including Cosmopterix clandestinella Busck , Cosmopterigidae , in the same host plant, in this case using a single hole at one end of the mine), I believe this is the first record of any North American beetle doing so. Hering (1951) stated that this habit is restricted to Lepidoptera , but Hespenheide and Dang (1999) reported Costa Rican hispines in multiple genera with similar habits. Species of Octhispa Chapuis , Platocthispa Uhmann , and Sceloenopla Chevrolat were specifically recorded as having holes or slits at the mine margin for voiding frass, and species of Baliosus Weise , Oxychalepus Uhmann , Sumitrosis Butte , and Xenochalepus Weise also had mines that lacked frass. None of these beetles were reared from grasses, but the authors noted that collections of mines had largely neglected grasses, resulting in a disproportionate scarcity of Chalepus rearings.

I saved the leaf in a plastic vial, and after about a week the larva exited the leaf, having mined out about 12 cm 2. It showed no interest in entering a fresh leaf it was offered. I transferred the larva and the fresh leaf to a small jar of soil, and by 10 July the larva had pupated on top of the soil. The adult emerged by 20 July. Apart from my observations of B. nervosus , I know of no other record of a hispine exiting its mine to pupate. Having reared just this one C. bicolor adult, I cannot say with certainty what the normal habit of this species is. I collected two identical mines in Sturbridge, Massachusetts on 6 July, but the larvae died when fullgrown—one inside its mine and the other outside.

In a completed mine, a large terminal portion of the leaf is entirely brown and most of the frass has weathered away from the edge.Thus, the damage may not be recognizable as a leaf mine to a casual observer.

Figures

Figs. 1–6. 1) Baliosus californicus mine in Ceanothus velutinus leaf; 2) Leaf mine in black oak (Quercus velutina) with section of upper epidermis removed to reveal two Baliosus nervosus adults and larval frass pattern; 3) Detail of Baliosus nervosus mine in black birch (Betula lenta) leaf, with ragged hole at lower right; 4) Chalepus bicolor larva mining in deertongue grass (Dichanthelium clandestinum), with frass expelled along the leaf margin; 5) Feeding sign of Chalepus walshii adults; 6) Glyphuroplata pluto larva mining in Panicum leaf, with frass in long strands.