To Each Her Own

Last week I had the pleasure of watching a female Gulf fritillary butterfly dance around the yard, looking for just the right place to lay her eggs. Gracefully she went from plant to plant, searching for the exact one that she needed. She landed many times, only to lift off again in just seconds when she realized it was the wrong one.

Gulf fritillary looking for nectar on Joe pye weed

Laying an egg (not much time to focus the camera!)

Finally, she found it. She found the passionvine (Passiflora lutea). That was the one she wanted. In a crazy, acrobatic move, she grabbed not a leaf, but a slender tendril (which is actually a modified leaf). She bent her body to it and laid a single, golden egg. Then she took another spin around the area, found another tendril, and laid another egg.

Left side: New egg  /  Right side: 2 days later

Passiflora lutea

How amazing is it that this small creature, just days out of her own chrysalis, knows just what to do? If she lays her eggs on any other plant, they will perish, unable to get any nourishment. Gulf fritillaries have evolved to eat only passionvine (Passiflora), just like monarch butterflies eat only milkweed (Asclepias).

There are several species of passionvine native to Georgia. The large purple one (P. incarnata) is probably the most familiar one. The one in my yard is much smaller, with a pale yellow flower. The vine is quite prolific, though, and it scrambles all over several shrubs. The fruits are small and dark blue, almost like an olive.

Since I saw where she laid the eggs (on my front porch, where the vine had sprawled), I was able to check on them with my hand lens. After a day, they started to darken, evidence of the growing caterpillar within. After 3 days, the first one hatched and climbed up the tendril to find a leaf. The tiny dark caterpillar was only visible because I was looking for it!

The first day it could only eat one side of the leaf, leaving a translucent hole like a tiny window. By the second day, it was making real holes but not big ones. Then another one hatched and crawled to its own leaf, bypassing the leaf occupied by the first one. How did it know to do that!

Two caterpillars, one still very tiny

I was nervous leaving them there. The plant was blooming and the flowers are apparently very popular with a medium-sized wasp. Wasps like to feed caterpillars to their young. I imagined these caterpillars falling prey to a wasp, so after a few days, I moved them to my caterpillar cage for protection. They were growing very well until I noticed that a few of them seemed to be dying. A friend said they might have a disease, so I removed them and cleaned the cage.

The remaining caterpillars are growing larger every day, occasionally pausing to transition to a new instar and shed their skin. Soon they will be attaching themselves to the upper part of the cage and developing a chrysalis in preparation for their final transformation.

Then the cycle will start again. In fact, these two were found in the garden several days ago, in the process of making more eggs.