Failure to grow?

[Farfalla]

I have a caterpillar that SHOULD be in the chyrsalid stage with his 7 other brothers and sisters. However,it is only the size of a 2d instar caterpillar.
I witnessed him/her shedding yesterday. ( prior to that I was not certain if it ever did)
And it has not changed in size! The color of the caterpillar is much, much darker. The black stripes are very prominent. It is still eating.. just NOT growing ! ( I do note that although it is eating milkweed.. it has not eaten it's shed skin.)I was wondering if anyone else has experienced this phenomena and knows what the disease/issue is?

~Hope

[Gwynne]

I would separate him from the others. I had a runt that looked fine, just small. Jim advised me to separate him. I did and the next day he died. Cant tell you the reason. just that I had a similiar experience. For the recond, most caterpillars I can get to the chrysalis stage. It is then that I have all these problems.

I have a long skinny one. Wondering what is up with that?? Anyway ever have one like that? I figure caterpillars come in all shapes and sizes.

[Farfalla]

I keep all my caterpillars separate.( A little extreme..I know...But this way I don't have to worry about cross contamination.)
It's just the oddest thing I have ever seen.. and it does not fit any sort of illness I can find .

[Gwynne]

I am beginning to think that these monarchs are so delicate. I have no problem getting them to form a chrysalis. A good percentage of my eggs hatch. Most of my caterpillars form chrysalises. It is there that I have my problems. Tachinid fly, possible OE, failure to fly, failure to hang on to the chrysalis, so many deformed because their wings didnt dry correctly. The more I tried to help them find something to cling onto, the worse they were!