Spring azures fluttering in the woods

by KEVIN STRAUSS

Now that spring has finally arrived, our butterflies are making up for lost time. Spring azure butterflies are filling the woods. These small (one-inch wide) butterflies have powder blue wing tops and speckled white underwings (females are darker). The spring azure (also known as the “common blue”) is one of the most widespread butterflies in North America. It can be found in forest, forest edge and scrub habitats from coast to coast and from the subarctic treeline to the tropics in Panama.

The fall generation of this butterfly hibernates in its chrysalis (hard-shelled butterfly “cocoon”) throughout the winter. The spring azure is the first butterfly in our region to emerge from its chrysalis in the spring. And once they emerge, it seems like spring azures don’t stop moving. That’s probably because adult spring azures only live about a week or two, just enough time to mate and lay eggs on dogwood, blueberry, cherry and viburnum shrubs. The female spring azures seem to choose a different plant species for her eggs depending on what is flowering at the time. Eggs laid in early summer will hatch and the caterpillars will feed, form a chrysalis and become adults this summer. Those adults will quickly mate and lay eggs to start the cycle again. Eggs laid in the fall take a different path. These caterpillars hatch and begin feeding on food plant leaves. But then the story takes a turn. This generation of spring azures forms a chrysalis and stays there throughout the winter.

Unlike larger and slower butterflies like the monarch, spring azures don’t have chemical defenses that make them taste bad. They also don’t look like any of the butterflies that taste bad, so birds are often looking for a spring azure to eat. That is why azures use fast, erratic flight to make it harder for predators to catch them.

But it is not only the adults that need to worry about predators. The slow-moving caterpillars are in danger as well. Spring azure caterpillars, like most larvae, are basically tube-shaped eating machines. They don’t have many physical defense to protect themselves from the many insect predators who might want to eat them. But azures, like small European nations, have a defense: allies. Ants often discover the caterpillars and care for them, protecting them from predators until they form a chrysalis. The ants aren’t doing this just out of kindness. This caterpillar excretes a kind of sugary “honeydew” that the ants feed on in return for their care and protection. If a caterpillar detects an approaching predator, it can release a chemical from its body that attracts ants and makes them wildly aggressive toward insect predators.

So while you are outside this week, look around for these tiny blue fast-flying butterflies. If the spring azures are out, it must be spring!