Melolontha melolontha L Cockchafer

Larvae of this large chafer occur mainly in grassland, although the adults tend to be most numerous in association with forests, woods and hegderows. The larvae are capable of causing considerable damage, as they bite through the roots and burrow into other subterranean parts of plants. Cereals, hop, lettuce, potato, strawberry and sugar beet are particularly vulnerable, especially when such crops are planted in recently ploughed-up pasture. Adult cockchafers graze on the foliage and flowers of shrubs and trees and are considered important forestry pests. The adults also attack developing fruitlets of fruit trees, removing parts of the flesh; bites sometimes reach down to the core. Chafer-damaged fruits either fall prematurely or remain on the tree; in the latter case, the injured tissue heals over and, depending upon the degree of injury, develops into corky patches or pits. Similar fruitlet damage is caused by caterpillars of pests such as clouded drab moth, Orthosia incerta (p. 243), and winter moth, Operophtera brumata (p. 231).

BIOLOGY

Adult cockchafers are active at night in May and early June, and are often attracted to lighted windows. They feed on the foliage of various shrubs and trees. They often roost in trees and bushes during the daytime and remain in a comatose state even when disturbed. Eggs are depos ited deeply in the soil, usually at a depth of 60 cm or more, typically in batches of 12-30. They hatch in about 6 weeks. Larvae then feed on the subterranean parts of plants for up to 3 years before becoming fully grown, passing through three instars. They then pupate, usually in their third summer, each in an earthen cell. The adult stage is reached about 6 weeks later, but individuals remain in the pupal cell and do not emerge from the soil until the following spring. Mass emergence of adults often occurs at regular intervals, e.g. every 3 years, coinciding with the main local developmental phase of the larvae.

DESCRIPTION

Adult 20-30 mm long, pale chestnut-brown with a darker head and pronotum; elytra partly clothed in whitish hairs; abdomen protruding beyond the elytra and terminating in a blunt spine; antennae with six (in female) or seven (in male) lamellae. Egg 3 x 2 mm when newly laid, yellowish or whitish. Larva up to 50 mm long; body mainly white and sac-like; head brown; anal segment translucent, the anal slit wavy, transverse and surmounted by two longitudinal, parallel rows of spines (Fig. 203c).

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