Monocesta coryli

Family: Chrysomelidae

Subfamily: Galerucinae

Length: 10-16 mm

 

The Larger Elm Leaf Beetle feeds almost exclusively on elms, including American Elm, Slippery Elm, and others. One researcher has reported that last instar larvae sometimes attack nearby hawthorn shrubs, particularly if the Elm leaves in the area have been devoured.

The Larger Elm Leaf Beetle is one of the largest members of the family Chrysomelidae found in West Virginia. They have a plump appearance, and the elytra are broadest toward the rear.

This species varies considerably in the amount of the bluish-black color present on the elytra. In some beetles there are two large bluish black areas, with a middle band of the yellowish color. On others the yellowish color dominates and there is almost none of the dark.

The species specific name, coryli, refers to Hazelnut, and reflects an error of the first collector of this species. That first reported specimen apparently was resting on a Hazelnut leaf, but neither larvae nor adults have been observed feeding on hazel, nor will they feed on Hazel leaves in the laboratory.

Monocesta coryli is the only species in the genus Monocesta that lives in the United States or Canada, though about thirty other species live in tropical areas of the Americas. No Monocesta species are found outside the New World.

Anderson and Papp (1961) are among several researchers who have studied the life history of this species. They describe how "The full-grown, reddish-brown, metallic-lustered third instar larvae overwinter in cells a few inches below the surface of the soil." The insects begin pupating in early April and pupation lasts 12-24 days. After emergence, the adults mate in June and oviposition comes in late June and early July. The yellowish masses of eggs are attached to the underside of Elm leaves, contain 30-50 eggs and take 7-15 days to hatch.

Anderson and Papp found that the first instar lasted 3-11 days, the second instar 8-15 days, and the third instar lasted 8-20 days above ground, followed by months under the soil as mentioned above.

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