Bulletin . , Piois rapae, for example, I have known to. Fig-. 17. Goatweed Butterfly. Sketch by Will C. Collins. lay eggs late in June. Caterpillars hatched from these eggson June 20th, were full grown on July 9tli. Pupae formedon July 9th, emerged on July 17th. The imagoes thus formedwould undoubtly have lived not more than ten days ortwo weeks. The average life of an imago, summer brood, isabout two weeks In this case, the life period, from the -32- hatchin<r of the egg to the death of the imago, does notexceed five weeks. Take another illustration. I have ob-tained caterpillars of the Go
Bulletin . , Piois rapae, for example, I have known to. Fig-. 17. Goatweed Butterfly. Sketch by Will C. Collins. lay eggs late in June. Caterpillars hatched from these eggson June 20th, were full grown on July 9tli. Pupae formedon July 9th, emerged on July 17th. The imagoes thus formedwould undoubtly have lived not more than ten days ortwo weeks. The average life of an imago, summer brood, isabout two weeks In this case, the life period, from the -32- hatchin<r of the egg to the death of the imago, does notexceed five weeks. Take another illustration. I have ob-tained caterpillars of the Goatweed Butterfly, A/uea a/nirni,(Fig-. 18) from eggs laid late in August. These pupatedlate in September; and the imagoes emerged earh inOctober. It is well known that the imago hibernates. AtNashville, Tennessee, imagoes which had wintered over werefound to survive as late as June. Here the life period isnearly a vear. That of the summer brood, however, is onljabout six weeks. This problem of the difference in durationof the life periods can be solve
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