Malformed Monarch Butterflies

I have some questions about what may have causes deformities in my monarchs this year. I had two somewhat normal ones hatch, and one with tiny wings. One of the normaler looking ones was really disoriented. The other normal sized one died before I could observe its behavior. those two died, and now this third tiny winged oddball hatched and I think is just unable to pump the fluid from his abdomen into his wings. he is still alive so far.

For context, I raised eleven monarch larvae and for the first part, they lived in my house which was air conditioned. the babies all did great, and pupated, and my first few adults emerged without trouble and were released. We had to go on a trip, and I still had many pupae left, so I left the mesh cage outside in the shade unzipped, thinking that the butterflies would hatch and then fly out.

There was a weird temp change when I was gone, and the heat spiked unexpectedly. When I got home, many of the ones who hatched were still inside, so I placed them on flowers and they flew off. I was left with these last three, one of which was dead when I found him. The other, a female, couldn’t even walk and kept flipping over. And the last one, another male, has tiny wings and… I honestly dont know what to do with him.

I also have one more pupa and Idk if moving it back in will just make it worse, bc of the sudden temp change.

What could have caused this, was it the heatwave? I wish I had done something different, this last guy is just so sad looking. This has never happened before, and I have been raising these for years.

did you already check for OE infection?

What is that, and how do I check for that? EDIT: Looked it up, yikes, I have the two dead ones in a sealed ziplock and they do look a bit like they could have it. I will also check my remaining pupa.

here’s a page that has decent information on DIY testing. you basically need a microscope, clear tape, and a white card or piece of paper.


Only 17 observations so far, only a few of which show the host butterfly.

Done, the little one was fine, the two dead ones might have OE, I might submit those on iNat to be sure.

New question, as I found presumably one of mine dead in our yard this afternoon (likely from a young bird who will learn a lesson, lol):

Can you pin monarchs in MI? I couldn’t find anything online, so maybe someone here has that info.

Also: thanks again to @pisum for all the help! This OE test is interesting. The last one, a female, hatched this morning and she was fine, so now I will just clean the cage and save it for the next season!

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