Disease in Cecropia larvae????

[Emily]

This is my 4th year rasing Cecropias in Minneapolis, MN and every year
something different goes wrong. This summer I started out with over 200
caterpillars (I underestimated the number that would actually hatch and
survive from the eggs I had) but now I am down to 8 caterpillars still
alive, and three more of them are dying right now.

Something is killing them all. They are in their 3rd, 4th, and 5th instars
right now but they are still very small, and they are dying one after
another. One of my caterpillars will be doing fine and then something will
come over it, and it will start vomiting (I swear this is true, I saw this
happen) green and brown liquid and little specks of leaves that it ate, and
it will start turning brownish underneath its skin, and roll and squirm
around; it appears to be in a lot of pain, and then finally, usually by the
next day, it will be dead. The dead larvae are discolored grayish-brownish
green (or yellow in the case of younger ones) and squishy feeling.

I quarenteened my remaining caterpillars in individual containers, hoping
that if it is a contagious disease, maybe some of them would live, but they
are continuing to dye. By tomorrow I will be down to five out of over 200.

As I mentioned this is only my 4th year raising them, and my first thought
of what could have happened is the fact that I had all the catepillars in
one big screen cage outside when they were smaller. It is a large cage, but
perhaps not large enough for the number of caterpillars I started out with,
and maybe having them too crowded could have made them more suseptable to
disease. I didn't realize at the time that they could be over crowed; they
were so small and it was such a big cage but it's possible. I've been
keeping them clean and giving them fresh food so I wouldn't think that would
be a problem.

Another thought was some kind of mites or something, because when I would
change their leaves outside I found all these little tiny mites or something
crawling around inside the bottom of the cage and on my patio. But since I
moved the larvae all into individual containers, I haven't seen any of these
mites or whatever they are, and the caterpillars are still dying, so it
makes me think that maybe the mites were just something that was roaming
around my patio, and not bothering the caterpillars. I never found any of
them in contact with any of my caterpillars.

The caterpillars had been in a screened cage so I don't think they could
have had any contact with any parasitic wasps. I think it must be a virus
because their is no evidence of any other visible organism attacking them.

I was wondering if anyone else has had a similar experience, or knows of
anything like this happening. If so, I would greatly appreciate any
information or advice you could give me.

Thanks
Emily