Phyllotreta chalybeipennis (Crotch, 1873)

Eiseman, Charles S., 2015, Notes on Leaf-Mining Chrysomelidae (Coleoptera) in New England, The Coleopterists Bulletin 69 (3), pp. 453-458 : 456-457

Phyllotreta chalybeipennis (Crotch, 1873)

This species has long been known to mine leaves of sea rocket, Cakile edentula (Bigelow) Hook. (Brassicaceae) ( Frost 1924), but it appears that no details have been recorded. I collected larvae mining leaves at Eel Point, Nantucket, Massachusetts (41.296422° N, 70.196893° W) on 26 July. The larvae were slender and yellow with dark spots, about 5.5 mm long when mature ( Fig. 11 ). Their whitish mines were irregular in shape, sometimes linear ( Fig. 12 ), but typically more or less blotchy ( Fig. 13 ). They were mostly visible on just one leaf surface, usually the upper, but I observed at least one lower surface mine. Occasionally, small patches of mines were fulldepth and transparent. As seems to be the case with most leaf-mining chrysomelids, the larvae were able to exit and establish new mines, and they frequently did so. Mines of two or more larvae sometimes merged. The dark frass was distributed randomly, sometimes forming a lumpy mass and sometimes in scattered discrete, tiny pellets. The linear portions tended to have little or no frass. Of the 10 larvae that ultimately burrowed in soil, seven emerged as adults on 14 August, two on 19 August, and one on 21 August.

At the time that I collected the larvae, I also collected two specimens of the many adult Phyllotreta Chevrolat that were feeding on foliage of the host plants. One of these was P. chalybeipennis , but the other turned out to be Phyllotreta cruciferae (Goeze) , larvae of which are root feeders rather than leafminers ( Knodel and Olson 2012). At least a dozen thrips ( Thripidae : Thripinae) were living in one of the abandoned P. chalybeipennis mines. Two of the leaves I collected had mines of an agromyzid fly, likely Liriomyza brassicae (Riley) . To the naked eye, these were difficult to distinguish from the linear mines made by younger P. chalybeipennis larvae, but when backlit and viewed under magnification, the fly mines were identifiable by the distinct strips of frass along alternating sides of the channel.

Figures

Figs. 9–13. 9) Larva of Mantura chrysanthemi; 10) Larva of Mantura floridana; 11) Larva of Phyllotreta chalybeipennis; 12) Mostly linear mine of P. chalybeipennis; 13) Blotch mine of P. chalybeipennis, with one larva inside and one entering at right.