Larch Casebearer Moth

Coleophora laricella produces one generation per year with four life stages egg, larva (with four instars, or growth stages), pupa and adult.

Egg. Adult females produce 50–70 eggs, deposited one at a time on the needles of the larch. New eggs are a bright yellow colour, but they later turn burnished red. Eggs have 12 to 14 ridges extending from the top to the base of the egg. In areas with dense C. laricella infestations, females may deposit as many as 10 eggs per needle. Eggs hatch in about two weeks.

Larva. Larvae are 5–6 mm long, hatch in July, and pupate about 11 months later. The first and second instar larvae hatch and bore directly from the egg into the needle, and mine inside the needle until August or September, during which the hollowed out needle is converted into the distinctive case. Once the case is created, the larvae progress to the third instar during which the case is fastened to a new needle with silk. The larvae continue to mine the needles discarding old cases as new needles are hollowed out and converted. In October, the larvae prepare for winter by attaching their cases to more solid parts of the tree (twigs, bark, etc.). When spring comes and the larch refoliates the larvae molt into the fourth instar stage and continue mining.

Pupa. The pupal stages lasts for about two weeks late May or early June. …