This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
One frequently finds a reddish larva in plums and gages when ripe. This is the caterpillar stage of a small moth called the Plum-fruit Moth (Opadia funebrana). The moth (fig. 364) appears in June and July. The female lays her eggs at the base of the stalk, and the larvae on hatching enter the fruitlet. The moth is 1/2 in. in wing expanse; the front wings are purplish grey, clouded with smoky grey; at the anal angle is an indistinct ocellated patch edged with shiny pale grey and enclosing four black dots. The larvae feed on the inside of the fruit, especially around the stone. The colour varies from red to chestnut red with yellow sides, and some of the segments have dark spots. In length the larva is about 1/2 in. When mature they leave the fruit, and many fall to the ground; if so, they reascend the trees until they come to some shelter. The winter is passed in the larval stage under any shelter, mainly on the trees, such as under cord, shreds, rough bark, etc, in a cocoon very similar to that of the Codlin Moth. In spring they pupate in this cocoon.
There is no method of destroying the creatures when once inside the fruit, but the larvae may be trapped in large numbers by placing pieces of manure sacking around the trees, the same as is recommended for Codlin Moth. The bands may be removed and burnt in winter with the hibernating larvae and cocoons caught up in the sacking.