I’ve had a few people write or call me upset that their Monarch Butterflies either did not form a proper Chrysalis or that the Butterfly was born with deformed, crinkled wings. Today, I had the same experience (it’s happened many, many times). I thought I would take a moment to comment on my understanding of why this may happen.
First, the image below is a picture of the Butterfly that we found in the yard today, unable to fly, and with deformed wings. There’s not really much you can do if the Butterfly cannot fly, although in the past I have raised one that did have this condition and somehow it mated (a male Monarch attached itself while the Butterfly was feeding on Milkweed), laid eggs, and had many offspring. You can read the multiple stories about this adventure of “Timothia” by clicking here, and reading from the bottom up.
My understanding of why this can occur (as why as Monarch caterpillars fail to form a Chrysalis) is related to several factors. One of the most common is due to the OE (Ophryocystis elektroscirrha) parasite. Before I go further, for good explanations of OE, I recommend The University of Minnesota’s Monarch Lab. Unfortunately, this parasite is very common (I think I recall up to 70% of Monarch Butterflies in the South). In layman’s terms, this parasite essentially weakens the Butterfly or Caterpillar and often the Chrysalises fail to form, turn brown, or results in a Butterfly with deformed, crinkled wings. There is loads of information on the web about how to test a Butterfly for this parasite (yes I have and do, do this) and a microscope. Since I know folks don’t tend to want to read long blog posts from me, just do a search for Monarch Butterfly OE Disease.
What has also been a somewhat common occurrence is when Monarch Caterpillars fail to form a Chrysalis. Besides OE, Monarchs can be attacked by the Tachnid Fly. Again, you can do a search on that term, but what happens in my experience is that Monarch Caterpillars that fail to form a Chrysalis (just hanging limp from the original “J” shape), or the Butterfly fails to form from the Chrysalis. In both of these instances, you may notice a long white string emerging from the Caterpillar or Chrysalis, and eventually you’d see these little fly larvae (it’s as gross as it sounds).
There are other diseases and parasites that can affect Monarch Butterflies and Caterpillars, but those are two of the most common in my experience.
If you read my stories on “Timothia” you’ll see that was quite a series of events (almost miraculous), but I wouldn’t advise doing that now. The reason is because it likely just spreads further diseases among the Monarchs, and they need all the help that they can get. When I have a deformed Monarch with crinkled wings, I simply place it in a plastic bag, then place it in the freezer. It’s the most humane thing I can think of to do.