Yikes!

Could be a weird virus, too...were there any flowers in with the caterpillars? I mean, if the larvae eat flowers, then the frass will be a different colour. Have any of the larvae become a mushy mess? If so, then a virus attacked them from the inside and that's what caused the explosion. Usually a virus will attack from the inside-out and cause 'explosions' like this whereas a bacteria will sort of just disintegrate the larva. If a viral-infected caterpillar is touched by something, it could explode.

Your poor little 2-year old...

When it rains, it pours! I hope she feels better.

Well I got everyone in new containers, with fresh clean milkweed. I ended up using my Butterfly Weed, I even soaked in a 5% bleach solution.

I'm pretty sure they were poisoned, whether it be the milkweed, or the tiniest bit of overspray I don't know. When I checked the lil guys, there were 17 last night, only 10 this morning. Same thing, green spew. I found 4 dead, 3 missing. In another container there were 2 1st instars I found outside. They were affected too, just differently. They are the size of 2nd instar, but I don't think they molted. They are swollen to the point they are shiny, and are transparent enough to see the green inside.

I don't think it is a sickness because why would all containers have the same problem? I collected from 5 or 6 different mw plants yesterday, in differant areas. My personal opinion is that even though I didn't notice any over spray from the orchard, their might have been just enough carried up front to get them sick. (Come to think about it, my first batch that had the green spewing issues, the orchard sprayed w/ in a week before that too.) Not all the lil guys seemed to have been affected. after I put them in a new container, and gave them new mw, some are crawling around the egdes, sick like, while others climbed right up and started munching away. The 2 5th instars that made the huge mess, are still spewing, I'm gonna give them till tonight to see if they improve. I seperated the guy that just molted into 5th instar to his own jar. He seems perfectly fine.

I just feel soo awful! I poisoned all my cats.

I'm still curious if anyone know anything about older milkweed plants becoming toxic to cats?

Looks like you responded while I was posting an update. The 2 larger cats don't look injured or anything, well they do look sick, antenae limp. The frass is a lighter green than normal, usually it's pretty much black. No flowers or anything else in the cage. I did notice however that one of the 5th instars when I went to take him out of the cage, was eating the paper towel, where there was dried puke! I got him off the paper towel and into a new container, but I don't think he's gonna make it.

Out of curiousity, I did a web search for apple orchards and poisoning caterpillars, I found this site that talks about a new environmetally safe way to control the apple orchard caterpillar pests.

"The system starts by spraying trees with Bt (Bacillus thuringiensis) toxin a bacterial product collected from culture that exclusively targets and kills caterpillars. A compound that mimics a caterpillar growth hormone is then released to slow or arrest the pests growth and maturation. The last step involves exposing the insects to a fermented yeast product that can act as a caterpillar stomach poison."

"Two other potential compounds for fighting caterpillar infestations include a virus that specifically infects leaf-rollers and a hormone analogue that interferes with normal caterpillar reproductive cycles."

I wonder if that's what I'm dealing with? I understand that they need to protect their crops, and we chose to live backed up to 800 acres of apple orchards. So don't get me wrong here, I'm not complaining about the farmers (i asked a question on the orchard forum this spring about the sprays and was attacked, all I did was ask a question)

I find this particularly sad, because the other day when the kids and I went for a walk in the orchard, we found this ENORMOUS patch of milkweed. It was an old row, w/ apple tree stumps, that overgrew with nothing but milkweed. Never seen so muchin one spot. All those cats... And they got a direct spray. The farmer has been turning down the spray as he passes our yard, so I'm thankful for that consideration.

It sounds like what I have had a couple times, and I was told by Edith at Shady Oaks it is called Melt. Are your pupating cats still there? If the aren't that is what it is. What happens is the cats go into the j shape, but they can never shed their skin. Instead they start drooping more and more until they are just hanging by their skin, and they rest of their body seems to be towrds their head. Eventullay the will drop nad of course explode. It is horrble, because they will go like that, one after the other. You will need to keep any cats that have come in to contact with the plant that you got the leaves off of, and either cut down or wash the plants with the bleach solution as you did. If you dont end the cycle now, it will continue.

Well I did some more research, and according to our local agricultural site, my area (not just this orchard, all) are scheduled to spray BT between 7/15-7/30 and again the mid-end aug.

One of the 2 5th instars died, the other has been getting slower and slower moving, and he just finally stopped and curled up, still alive, but can't move much. I'm off to euthanize. I also lost a few more 2nd instars, and think a couple more are on the way. I did seperate the healthy, munching away ones from the slugish, still spewing ones.

Now that I'm pretty sure I know the cause, I need to figure out a way to prevent it again. Obviously the overspray affects further into my yard than anticipated. I do have my butterfly weed that is planted right in the corner where my garage meets the house (its attached, but in front of.)and has the porch on the other side of it. I'm fairly certain it didnt get hit.

gatorgyle- you must've posted same time I did. My pupating and chrys. are all fine, no problem. It's just the ones that ate the milkweed I gave them last night. Like I said above, the apple orchard I live backed up too, sprayed yesterday afternoon, and I'm fairly certain they sprayed BT. I knew they sprayed when I collected mw, but I thought I collected far enough away that it didn't get hit. Plus I washed really well. Obviously, I thought wrong, and am now feeling like this evil terrible monster, especially when the largest of the affected would rear up and do that circley motion w/ his upper body like he was screaming in pain, when ever I checked on him. I swear I heard him screech too! Do monarch cats make noise? I know the tom and tob horn worms do, makes it easier to find them.

Alright, I'm done tormenting you all with my awful day! Oh, by the way, my daughter has been fine all day, just that one explosion this morning...probally too much juice yesterday.