Air conditioning and tick and flea medicine. Keep containers away from both.

Where are you getting their food? Does your area spray for mosquitoes? The mosquito fogging trucks have started, and if your food source is hit with the fogging chemicals, it will kill your cats. Anything within 40 - 50' from the road can be affected.

No A/C, no flea and tick chem, and no spraying schedule.
The food comes from my front and side yards and also down the street.
So far, knock on wood, only the one enclosure was affected. The other cats seem to be fine. The only difference is that those cats were raised on Swamp Milkweed and the others are being raised on Common Milkweed.

John

i might be wrong but cats wonder around and pulsate before cacooning. try to switch the food items around. what kind of cats?

This really does sound like pesticide. Your down the street source may be poisoned.

I wash my caterpillar's food with the sprayer in my kitchen sink before feeding it to them, in case there could be small bugs on it I didn't see, or, even though I'm a long way from my neighbors, they may have used a pesticide that could have traveled by air this far. If you're living in a typical neighborhood, your neighbors' use of pesticides would be even more likely to get on your host plant food, so if you wash your caterpillar food, that might help.

It may be that they've got some type of virus.

Are you having cool/cold night time temperatures? I've had a few cats die in early spring when the nights were real cool, whose deaths couldn't be attributed to anything else.

I'm so sorry about this, John!

Sherry