Many butterfly chrysalises have deformities that never make a difference in the adult butterfly. The other deformities cause minor issues, serious issues, or death.
(Side note: the chrysalises/pupae are placed on these trays to move them to the next lab, where they are either shipped to exhibits for them to emerge or we emerge them. They are not emerged like this.)
With the thousands of Monarch chrysalises we raise every week, we occasionally see deformities. A study of these deformities revealed which deformities are serious enough that the chrysalis should be euthanize and which are safe to release into nature. We do not like to euthanize a butterfly unless it is necessary.
When a caterpillar is a few days from pupation, it already has adult legs, wings, proboscis, and antennae. Once it pupate, these body parts continue to form and mature.
Many chrysalis deformities are caused by one or more of these parts being moved out of place. If the misplacement isn’t serious, the adult will emerge with the expected deformity: missing legs, bent wings, crooked antennae, or other abnormal parts. If the misplacement is serious, the chrysalis either dies or, when it is time, the adult butterfly cannot emerge.
We decided to see the seriousness of different flaws in chrysalises. We wrote a number or letter on a plastic cup lid, laid the chrysalis on the lid, and took a photograph. The chrysalis was glued to the bottom of the lid. The side and bottom of the cup were lined with paper towel. The adult butterfly emerged and was placed in a special envelope and the cup number written on the envelope. Later that evening, after work was finished, the adult butterfly was compared to the chrysalis photo. A photo was taken of the adult butterfly and placed with the chrysalis photo. Before long, we were able to tell if a chrysalis had a serious deformity.
Some of these images are two images in one. To see each one clearly, please click on the image.
Some chrysalises looked normal except for a tiny mark on the proboscis area, but the adult butterfly would have a split proboscis. A split proboscis means that a butterfly cannot drink and will starve to death.
Others were clearly missing the tips of the legs, the tarsus (foot), the tarsal claws (hooks on the tips of the ‘feet’), had deformed or misshapen wings, misshapen bodies, bent or missing legs and/or antennae, and many other types of deformities.
Over the years, we have learned when we should euthanize a chrysalis and when we should allow the adult to emerge as a beautiful healthy butterfly.
One year, before we did this study, we saw a Gulf Fritillary butterfly in the garden. It was sitting on a zinnia bloom, drinking from the tiny yellow flowers. Every so often it would fall on its face, wings outstretched as if to catch itself. After taking photos of it doing this over and over, we picked up the butterfly only to discover that it was missing two legs. No wonder it had problems. But even with these problems, it continued to fly around the garden, drinking nectar from flowers as it landed and flew away again.