What's That Bug? does not endorse extermination

Subject: Beautiful Black Swallowtail & question
Location: Naperville, IL
September 11, 2013 5:32 pm
Hi Daniel~
All summer, I’ve been collecting the eggs that female Black Swallowtails have been laying on my potted parsley plants and rearing the hatched caterpillars. It’s always been my understanding that Black Swallowtails have two generations per summer – the first group ecloses in late spring after having overwintered as pupae. The second group is the product of the mating of the first, and they fly in late summer, mate, and lay eggs. All of these eggs that have hatched since late August should technically be the offspring of this year’s second generation, the caterpillars that pupate yet do not emerge until next spring. Well, the caterpillars that actually pupated in August, some as early as August 22nd, seem to be following that hypothesis; three weeks later, they’re still in their chrysalides and showing no sign of eclosing anytime soon. However, the caterpillars which pupated in early September, some as recently as September 4th, are eclosing now – all of them – just one week! The older ones remain pupae. I would attribute this to the record heat we’ve been having (high 90s), but they’re all being reared in the same conditions. If the high temperatures are fooling the younger pupae into eclosing now, why aren’t the older pupae doing so? What do you think?
Signature: Dori Eldridge

Black Swallowtail Emerges from Chrysalis

Black Swallowtail Emerges from Chrysalis

Hi Dori,
Your Black Swallowtail photos are gorgeous.  Alas, we cannot say for certain why the later group of caterpillars emerged first, but we suspect the warm weather might be playing a factor.

Black Swallowtail

Black Swallowtail

What's That Bug? does not endorse extermination
Location: Naperville, Illinois

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