catapillar mortality

[Judy Thoren]

Help, please. In twenty-plus years of raising butterflies I never expertienced mortality of catapillar such as I'm going through right now. Here's my situation....
I'm using 10 gallon aquariums, some with foll-schreen tops, some with plywood and screen tops. Inside I use a paper towel liner to cover the floor for easier cleaning. Aquariums are cleaned every night with fresh food put in. I sometimes wipe the inside glass clear of webs, and occasionally I wipe out the floor with dilute bleach water to counter-act odor.
Other environmental factors are air-conditioning with a constant 71 degrees. Ours is a smoke-free house.
The symptons I observe are one) a lack of eating, and two) lethary. After hatching they don't grow at the usual pace. They crawl onto the side of the aquarium and stay there and die.
The early summer batch of 500 catapillars had approximately 6-8 die, some by parasite. Now with the late summer batch I'm losing 12 per day in one aquarium. The other aquariums have some mortality, but minor compared to this one problem aquarium. Eggs and milweed have come from a variety of locales, so I cannot attribute the problem to a known problem location, but I never gather beside cornfields.
Death occurs at all stages, even changing from the "J" to a chrysallis. The catapillar body turns brownish and hangs in a "V" with only the mid-body feet attached to the glass. I sometimes notice a yellowish/brown fluid secreted from the body onto the glass.
I clean areas of aquarium, cover, and tools with dilute bleach. I cannot transfer the whole population because of chrysallises attached. When I have catapillars out for cleaning I allow them to transfer themselves to new leaves before returning them to the aquarium. I see that some catapillar stools are red instead of the usual green.
Help! I really enjoy the process of doing this, but it's very discouraging after all the work to lose so many! With such a large first batch here in June I thought I'd have a banner crop for tagging this fall, but I've done only 59 so far.

[mommalepapillon]

I am sure this mystery has an answer but it is not evident to this neophyte...I'll be watching for replies

Best of Luck!

[Farfalla]

So sorry for your cat losses. So even after 20 years I can look forward to unexlained illness?

But wow.. the number of butterflies you helped put in the world must be amazing.

I am pretty new to this but I had several unexplained deaths this season too. Cats were walking off their food,expelling green fluid and then dying. I also had one that did not grow and shed as they others in "his" batch did. By the time he should have been a chysalis he still only looked like a 2d or 3d instar! Then he too finally died.

One thing you said.. about the cat hanging in a V....reminds me of something I read about Nuclear polyhedrosis virus ,but I can not find the reference.
I hope you find a more conclusive answer.
Not knowing ( and not knowing if it can be prevented) drives me crazy,too!

Maybe Jim or Scott will have an answer for you!

[Jim]

One thing you said.. about the cat hanging in a V....reminds me of something I read about Nuclear polyhedrosis virus

Yep - or at least some sort of virus. We're seeing that a little here as well in some cats that we are rearing outside for our Fall Open House coming up. These cats usually also turn dark and then black.

Red frass is nothing to be concerned about - red is typically the color of the "terminal" frass that the caterpillars excrete just prior to pupation.

Give your cats plenty of space, plenty of airflow and sterilize everything when you can using Oxine or a bleach solution.

Good Luck!

[Farfalla]

I never knew that about "terminal frass". Thanks for that info ,Jim.
Jim.. please create another photo essay of your open house! It's the next best thing to being there.

[sbowman]

I've seen a higher rate of mortality this year too, but from butterflies getting stuck in the chrysalis when attempting to emerge. I'm thinking it maybe they are getting a little dry in the house with the A/C running. We are a smoke free house and keep the temp at 78 degrees (this temp actually feels cool compared to outside temp of 95+ degrees with 100% humidity). I'm torn between bringing the cats into the house & chancing that problem with letting them live in the waystation & be a possible meal for the red wasps & fire ants. How much intervention should you do to protect the cats?
Sherry

[John Beaulieu]

We have lost quite a few caterpillars and some in the chrysalis stage this year, more than any other year. We have, however, found more this year than ever before, so the percentages are still good, especially considering how few make it when left in nature. When we collect eggs, we rarely lose any. It is just when we start bringing in the larger caterpillars that the losses go up. We assume that is because they are already aflicted with something, disease or predator. We got busy and never kept a good record, but feel that we have done about 300 monarchs this year. It is coming to an end now. I found what could be the last caterpillar from my milkweed garden waystation yesterday. There have been no new eggs for weeks now. We have about 12 chrysalises to go. When they emerge and get released they will be thinking "Gotta go, Gotta go, Gotta go to Mexico"!