Observations on the Biology and Behavior of the Evergreen Bagworm Moth, Thyridopteryx ephemeraeformis (Lepidoptera: Psychidae)

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Abstract
Females of Thyridopteryx ephemeraeformis (Haworth) usually oviposited in their own pupal cases, where the eggs remained in diapause until the following spring. Larvae, after emerging from the pupal cases and the parental bags, passed through 7 stadia in the laboratory, in about 3 months, in bags which they constructed. Exuviae were not eaten, but fell out of the bags or were pushed out by the larvae themselves. Ability to construct bags was limited to a brief period following eclosion. Positive phototropism apparently was involved in the reversal by last-instar larvae of their position in the bags, turning their heads toward the posterior bag openings. The pupal period averaged 18 days. Males emerged as active, free-flying moths; females, with vestigal mouthparts and legs, small eyes, and no antennae or wings, remained in the bags and became merely egg-filled sacs. Some, which had failed as larvae to reverse their position, did so upon becoming adult. This was necessary because pupal cases were only about half as long as the bags, and the bags were crisscrossed internally with larval silk which prevented the pupae from slipping to the posterior ends where the adult female would be accessible to the males. Mating, at best, was a difficult and complicated process; some males died clinging to the bags of receptive females which they had been unable to inseminate. Despite a sex ratio of about 1:1, only about 14% of the females were fertilized in the laboratory-reared generation. However, in nature, all the 21 females of the parent generation collected at Norman, Oklahoma, had been fertilized. Unfertilized eggs remained in the maternal body and appeared viable even a month or more after the parent's death, but eventually they degenerated. Adult longevity was 1–2 days for males, 4–9 days (average 8 days) for females.

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