cecropias- double brood?

[James J. Kruse]

Hello,

> I am raising cecropias, it is the middle of July and already I have some in
> the 5th instar. They seem to be growing faster than normal. At the rate they
> are going, the larger ones will be making cocoons soon. If they make cocoons
> so early, is there a possibility of a double brood, and if so, what will
> happen? I live in Minnesota, so I'm not sure what would happen if there is a
> double brood. I have never heard of this before with cecropias. Maybe there
> won't be though. Can anyone help me?
> 
H. cecropia have split broods in the upper midwest. Adults will emerge
in late-May and early-June, and then more will come out in late-June to
early July. The early group will spin up in late-July into August, and the
later group will usually spin up by early-October. These late ones are 
often brought by school children to class in the fall. When I lived in
Wisconsin, a female brought in 6 males on the 8th of July! Interestingly
enough, Callosamia promethea exhibit this same sort of split brood
behavior in the upper midwest as well.

They shouldn't emerge before the end of the summer, but if you are nervous
about it, you could refridgerate the cocoons a couple of weeks after
they are spun, then take them outside when the weather is cold. The moths
will emerge in the winter if kept inside. Also, cecropias typically take
around 50 days from egg to cocoon, so I doubt you could get them to
emerge, mate, lay eggs, have the eggs hatch (often 14 days in itself) and
then still have 50 days of leaves left on the trees, especially in
Minnesota!

Hope this helps,
Jim Kruse
University of California at Berkeley
Dept. of Environ Sci, Policy and Mgmt.
Div. of Insect Biology
Sperling Lab
201 Wellman Hall
Berkeley, California, 94720-3112
(510) 642-7410/5114
http://www.CNR.Berkeley.EDU/sperlinglab/sperlinglab.html