Spring officially arrived here in southern Indiana on March 14. We were just returning from a short trip and I parked the car in our driveway. Sandy stepped out of the car and suddenly said, “Azure!” She had flushed a beautiful male azure from the gravel, where it was undoubtedly seeking moisture.
Some butterflies in our area hibernate through the winter as adult butterflies. These include Mourning Cloaks and Eastern Commas, and you can sometimes see these two species flying around in the middle of winter during a warm spell when they briefly come out of hibernation. Most butterflies, however, hibernate either as chrysalises, partially-grown larvae, or as eggs. Those that spend the winter as chrysalises are the first to appear in the spring, since they do not have to wait for leaves of their host plant to appear before finishing their development, as those species do that hibernate as partially grown larvae. Species that hibernate as adults can always return to their hollow log to continue their hibernation if they guess wrong and winter weather returns. For species that emerge from a chrysalis, there is no going back—if they guess wrong and the weather turns cold, they die. So I have always felt that those butterflies that emerge in spring from their chrysalises, such as azures, whites, and swallowtails, are the true harbingers of spring.
Azures are usually the first butterflies we see in the spring that do not hibernate as adults. They are small, about the size of your thumbnail, and are whitish gray below and a beautiful blue above. When they fly around our yard or in the woods, it appears that a piece of the sky has fallen to our level.
We have two common species of azure in Indiana: Spring Azure and Summer Azure (there are two others—Dusky Azure and Appalachian Azure—that are very rare with restricted ranges). The Spring Azure only flies in early spring, the Summer Azure occurs in both spring and summer. These two azures are very similar in appearance. In fact, the Summer Azure was previously thought to be the summer form of the Spring Azure, but now there are known to be differences in larval host selection, flight period, and scale structure.
The Spring Azure (Celastrina ladon) has a single, early spring flight. Males are blue above, but have long, translucent scales overlapping their blue forewing scales, giving their forewings a “fuzzy” look. Spring Azures, and some other azure species that occur elsewhere in the U.S., occur in three color forms: “violacea,” “marginata” and “lucia.” All of these forms are blue above, they differ in the color and pattern of the underside of their wings. The form most often seen depends on the location. In Indiana, the typical form is “violacea,” characterized by its dark spots and hindwing border of dark chevrons.
The Summer Azure (Celastrina neglecta) does not occur in multiple forms and is typically slightly larger with a paler underside than Spring Azure. Summer Azures are most common in summer, but some adults do appear in the spring, and can be very difficult to distinguish from Spring Azures. Larval host plant association can be suggestive. Spring Azures are usually found flying near their host plant, Flowering Dogwood (Cornus florida), while spring-flying Summer Azures utilize Wild Cherry (Prunus serotina). (Both species lay their eggs on developing flower buds and the larvae eat the buds and flowers.) Spring Azures tend be darker below, with more pronounced hindwing chevrons, but for positive identification, males must be netted and examined for the presence of translucent forewing scales. On Spring Azures the scales are present, and the forewing veins will appear indistinct and fuzzy, if the scales are absent, as on Summer Azures, the wings will be bright blue with crisp, pale blue veins. Females, alas, have less blue above, with black borders to their wings, and can only be identified by association with the males. For magnified views of the azure’s forewings, see my book, Butterflies of Indiana: A Field Guide.
The azure Sandy flushed from our driveway hung around the rest of the afternoon and allowed me to obtain nice photos. It even landed briefly on the side of our house and opened its wings—revealing its blue scales and crisp veins—a Summer Azure!