One of the earliest butterflies to emerge in Indiana is the Cabbage White butterfly, Pieris rapae. Like most butterflies, they overwinter as a pupae. Adults emerge in the early Spring when their host plants in the mustard family are available for egg laying. Plants of the mustard family are typically cold hardy and are abundant in early Spring.
The females deposit eggs singly which spaces the eggs over numerous plants. When populations are large, a single plant can have numerous visits and dozens of caterpillars. The caterpillars, known as “imported cabbageworms” are common pests of cabbage. The caterpillars chew irregular holes in the leaves and open up cabbage to other infections. The caterpillars complete development in 2 – 3 weeks and 4 or more generations are produced each year in Indiana. A healthy population can wreck cole crops such as cabbage and broccoli if not controlled.
There are some parasitoid wasps that lay eggs in the caterpillars, but they rarely provide adequate control. The bacteria, Bacillus thuringiensis is often used as a natural control for the cabbage worms.
Most butterflies are not pests. They seldom produce large populations and they do not use our food plants as hosts. The Cabbage White is an exception. The Cabbage White is the most abundant butterfly in Indiana. The Cabbage White butterfly is native to Europe, not to North America. It was first observed in Quebec, Canada in 1860. It rapidly spread throughout North America. Large populations of plants in the mustard family are found in North America that provide plenty of food. Freed from many of its natural enemies, the Cabbage White can develop large populations.
Mated female Cabbage White butterflies spend most of their time searching for host plants and laying eggs. Males spend much of the day searching for females. Males are attracted to the females by their wing coloration and will approach the female to determine her interest. If the female is interested, they will mate. If the female is not interested, she will not respond to the male. If the male persists, the female will begin an upward flight. As the male follows, the butterflies will spiral upward together. The male quickly gets the message that the female is not interested, breaks off the interaction and returns to the ground. Once the male moves on, the female returns to her egg laying.
On a sunny summer day, we can watch this intricate dance performance in a field teeming with Cabbage White butterflies. Butterflies flirt, then spiral upward out of the foliage to soaring heights. Rejected, they return to the ground and carry on.