Western tentiform leafminer

Phyllonorycter elmaella

Eggs: Western tentiform leafminer eggs are small (0.3 mm in diameter), elliptical, and creamy to transparent. The transparency often makes them appear the same color as the leaf. Eggs are laid singly on the undersides of leaves and, depending on temperature, hatch in 5-16 days.
Larvae: Western tentiform leafminer larvae have five instars (stages), and their entire life is spent inside the mine, protected from the exterior environment. The first three instars are relatively small and are referred to as the sapfeeders because they feed on the sap from the spongy mesophyll layer of the leaves. The sapfeeders are flattened and legless, with an enlarged segment just behind the head, giving them a "broad-shouldered" appearance. In the process of feeding, they separate the lower leaf surface from the tissue above. During this stage, the mines are small, only visible from the lower leaf surface, and appear as light green lines or blotches. The fourth and fifth instars feed more on the leaf tissues and are referred to as the tissuefeeders. These larvae have a more typical lepidopteran larval appearance, with a cylindrical body, three pairs of legs on the thorax. The change in feeding habit and the increased size of the larvae make the mine visible from the upper as well as the lower leaf surfaces. It also gives the mines a tent-like appearance from the upper leaf surface, with small white spots where the green tissue has been removed. The lower surface will often develop a "seam" during this stage, where the tissue is bunched together longitudinally down the center of the mine. When full grown, the larvae are about 4 mm long, cylindrical, and white to pale green. Before they pupate, the larvae turn yellow. Larval development takes about 24 days to complete for the spring generation, but occurs faster during the warmer temperatures during summer.
Pupae: The pupae are 3-4 mm long and change from bright tan when first formed to dark brown. The pupal period lasts about 10 days for the first three generations and extends through the winter for the fourth generation. The pupa pushes out through the end of the mine, and the adult emerges from the pupal case, leaving it behind partially lodged in the mine. The pupal skin remains attached to the leaf for a time after the adult has emerged.
Adults: Adult moths are slender brown moths with distinct silver to cream colored bands on the upper wings Their length (2.4-4.0 mm) varies between sexes and generations. The moths that emerge in the early spring from overwintering pupae tend to be larger and darker than adults of the other generations. Mating and egg-laying occur in the evening. A female will lay an average of 25 eggs.

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