Plum curculio

Adult PC are typical snout beetles. They are dark brown to steely gray in color with patches of white or gray. They have four humps on their wing covers (elytra) and measure 4-6 mm in length. The beak or snout is 1/4 of the body length, with the mouthparts located at the end.
PC overwinter as adults in ground litter or the soil and become active in the spring following several days of either a mean temperature above 15.5°C (60°F) or maximum temperatures above 24°C (75°F). This time period normally coincides with the blossom period of apples. If temperatures drop and conditions become unfavorable the adults may return to hibernation sites. Although the emergence period for PC lasts for several weeks, 40-60% of the total emergence occurs on a single day.
Upon emerging in the spring, the PC fly to the trees where they feed on the buds, flowers, and newly set fruit. In feeding, the adult cuts a hole in the skin of the fruit and hollows out a cavity about 3 mm deep.
The beetles then mate. The length of the preoviposition period, following hibernation, is temperature-dependent and varies from 6-17 days. In egg laying, a female cuts a cavity under the fruit's skin with her snout. She then turns around and deposits an egg in the hole. Turning around again, she pushes the egg into the cavity with her snout. In front of the hole in which she has laid her egg, the female cuts a crescent-shaped slit which extends beneath the egg cavity so as to leave the egg in a flap of flesh. This protects the egg from being crushed by the rapidly developing fruit. Feeding and oviposition wounds on apples frequently exude sap that dries to a white crust.
The progeny of the adults that emerged in the spring appear as adults in July or August. They fly to the trees and feed on the developing fruit but do not reproduce in most instances. They are the adults that find hibernation sites in which to overwinter and produce their offspring the following year.