Why would a Caterpillar pupate, leave the skin attached to the top of the jar, and the chrysalis falls down? By the time I came home it was caved in and goo was coming out of it.
One of the caterpillars I raised from an egg to a full-grown adult ended up being a host to a tachnid fly larva-it popped out after the Caterpillar Pupated. I inspected all the leaves I brought in. I did not see any other eggs.
I keep the caterpillars in large jars with small holes punched in on the lid-nowhere near big enough for a fly to get in. I have been raising these guys for about six or seven years. I have never had a failure! This year I'm full of them.