Butterfly Chrysalis Deformities

Many butterfly chrysalises have deformities that never make a difference in the adult butterfly. The other deformities cause minor issues, serious issues, or death.

How serious are deformities in butterfly chrysalises?

Monarch chrysalises/pupae at the farm
Monarch chrysalises at the farm

(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.

Adult Monarch butterfly body parts are already partially formed before the caterpillar pupates
Adult Monarch butterfly body parts are already partially formed before the caterpillar pupates

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.

The proboscis had a space between the two sides.  When the adult emerged, it was unable to zip its proboscis beyond where this space began.
The proboscis had a space between the two sides. When the adult emerged, it was unable to zip its proboscis beyond where this space began.

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.

The tarsae (feet) of two legs were missing. The butterfly was unable to hold onto anything with those legs.
The tarsae (feet) of two legs were missing. The butterfly was unable to hold onto anything with those legs.

Some of these images are two images in one. To see each one clearly, please click on the image.

The brushfoot and middle leg on the right side of the chrysalis were missing. The adult was missing those legs.
The brushfoot and middle leg on the right side of the chrysalis were missing. The adult was missing those legs.

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.

Something punctured the left side of this chrysalis, through the wing. The adult had a hole in the wing in that area.
Something punctured the left side of this chrysalis, through the wing pad. The adult had a hole in the wing in that area.

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.

The tarsa (foot) on the left side of this chrysalis was missing, revealed in the adult once it emerged.
The tarsa (foot) on the left side of this chrysalis was missing, revealed in the adult once it emerged.

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.

A four-legged Gulf Fritillary butterfly
A four-legged Gulf Fritillary butterfly
The four-legged Gulf Fritillary kept falling forward as it tried to step forward.
The four-legged Gulf Fritillary kept falling forward as it tried to step forward.
The front two legs are brushfeet, pulled in tightly against its body, as is normal for this species.  It was living a normal life with only two supporting legs.
The front two legs are brushfeet, pulled in tightly against its body, as is normal for this species. It was living a normal life with only two supporting legs.