English: The Larch Casebearer lays its eggs on the needles of the Western Larch (and Tamarack). In a whole-year cycle of growth, the larvae burrow into the tree's needle-like leaves and form hollowed out shells in which to survive.n it's second cycle, the insect larvae construct this sheath around the needle they have moned, and then cut it free by chewing through the base of the needle. Much like a hermit crab, the larvae will then move around the twig looking for the next needle, carrying the sheath around their thorax elevated like a scorpions tail.