Chrysolina menthastri Suffrian Mint leaf beetle

This beetle feeds on wild Mentha and is sometimes a pest of cultivated mint. Individual adults or larvae cause little damage but, when the pest is numerous, attacks can lead to considerable defoliation.

BIOLOGY

Adult beetles appear from late April or early May onwards. They feed on the leaves of mint plants, usually devouring the edges. The beetles often rest in the leaf axils during the daytime but drop to the ground and feign death when disturbed. Eggs are deposited in raft-like groups, mainly in June and July; they hatch 1-2 weeks later. Although the larvae are not gregarious, and individuals disperse soon after egg hatch, several commonly occur on the same host plant. The larvae feed mainly at night and become fully fed in about 4 weeks; there are four larval instars. Larvae then enter the soil but do not pupate until the following spring.

DESCRIPTION

Adult 8-12 mm long, hemispherical, brilliant metallic green, often tinged with gold or coppery-bronze, and finely punctured. Egg 2.0 x 0.8 mm, creamish-white. Larva up to 10 mm long, shiny purplish-black to black; abdomen broad, fleshy and distinctly humped. Pupa 8.08.5 mm long, deep yellow.

swollen basal segment of tarsus

Fig. 215 Hindleg of wheat flea beetle, Crepidodera ferruginea.

Carduus, Cirsium, wild grasses and various other weeds, to feed in the coleoptiles and shoots of seedlings and in the basal tissue of older plants. They vacate those that rot or die and readily transfer to adjacent hosts. The larvae pass the winter in the soil and re-invade host plants early in the spring, to become fully grown in May. They then pupate in the soil and adults emerge about a month later.

Fig. 215 Hindleg of wheat flea beetle, Crepidodera ferruginea.

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