Reminder: After petting cats or dogs with oral (or topical) flea/tick medication, wash your hands well before touching caterpillars or their food. The medication is actually a pesticide that kills fleas and ticks. It gets into the dog’s body system, coming out in its skin oils and dander. When we pet them, we get it on our hands.
Some of the medications kill outright, causing caterpillars to vomit green and if it was strong enough, they die. Some of the medications cause improper pupation. Even others cause their mouth parts to work improperly, causing them to fail to eat well and they become weak and don’t grow normal.
You can learn more about the effects of flea/tick medication by clicking on this sentence.
Although chrysalises may be deformed due to other causes, flea/tick medication is one of the common causes for this problem.
Butterfly Fun Facts 
I had a chrysalis do exactly same thing. However we have no pets so flea/tick medication was not around. What could other possibilities be the cause? Out of 75 chrysalis only had the 1 deformed
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Anything from the wind or a critter touching the container/twig at the moment of pupation, genetic flaws, disease, and other things. Do you have a photo of it?
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Hi! My chrysalis looks the same as this picture and we also have no pets. The caterpillar has been healthy while it was growing, so I’m not sure what happened. Is there a possibility that it will continue to form and close properly? Thanks.
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