I'm just starting to have cats on my milkweed in Austin, TX. Given the seriousness of the drought & relentless heat, I've been trying to keep the plants tall & watered. The first cat I found had a second set of tentacles approx. 1/3 of the way down his body. He made it to about the fourth instar & died. Now I'm seeing more cats with the same deformity on other plants. Is there a known cause for this issue? There are so many factors - possible pesticide exposure (I'm careful, but not all the neighbors are), heat, drought, recent fires & smoke, genetics, diseases, parasites...
I guess the big question is, can this be managed or prevented in the unhatched eggs. Should I remove the mutants to increase the availability of food for other cats? My guess is that none of them will be able to make it to adulthood.

Think I might take a look at some neighbors milkweed & see if they also have mutants.