Summer 2003Meet Your Neighbors


Aphrodite Fritillary
Goddess of Butterflies

Even for a creature as lovely as a butterfly, bearing the name of an ancient goddess of beauty is a lot to live up to. No single feature or behavior connects the Aphrodite fritillary (Speyeria aphrodite) with the Greek deity Aphrodite, but as one of the showiest butterflies in Chicago Wilderness, this species is a celestial beauty in its own right.

 

The underside and top of an Aphrodite fritillary. Great spangled fritillaries have a wider pale band between the last two rows of silver markings on the underside of the hind wing. Photos by Randy Emmitt.


About the size of a monarch butterfly, the Aphrodite is tawny orange with black spotting on the tops of its wings. The undersides of its wings, ranging from tan to brown, feature beautiful silvery spots. These silver markings appear metallic, but they are actually made of specialized scales. The shiny, reflective color results from light scattering off these scales — a phenomenon known as structural color — rather than being partially absorbed by pigment.

The Aphrodite fritillary closely resembles the great spangled fritillary (Speyeria cybele), a much more common species. A simple trick readily distinguishes the two butterflies: the area between the silver spots on the underside of the Aphrodite is a rich reddish brown. In contrast, a broad pale band runs around the entire edge of the underside of the hind wing of the great spangled fritillary. The band (or lack thereof) is readily visible when the butterflies pause to sip nectar. With practice, butterfly watchers can even see this feature as the adults fly past.

Behavior distinguishes the two species as well: Although Aphrodites can be strong fliers, they are less skittish than great spangled fritillaries and seem to pause more often at flowers. Great spangled fritillaries typically spend more time flying, making them comparatively difficult to approach.

A single generation of Aphrodites emerges each year. Adults begin flying in late June and early July, males generally appearing before females. Although Aphrodites mate in midsummer, females do not lay their fertilized eggs until the end of summer, typically in the second half of August.

The eggs hatch a week or so after the female lays them. Newborn larvae consume their eggshells (a common diet for caterpillars) and immediately crawl under available cover to hibernate for the winter. They will not feed again until violets appear the following spring. As spring progresses, the active caterpillars develop rapidly, transforming into chrysalides in June. Aphrodites complete the cycle by emerging as adult butterflies right around the summer solstice.

The distribution of the Aphrodite's host plants, the violets, plays a role in where Aphrodites exist, but the picture is complex in ways researchers don't fully understand. In the laboratory, Aphrodite caterpillars can be reared on nearly any species of violet, but in the field, the butterfly remains much rarer than these species. In Illinois, Aphrodites inhabit only larger prairies such as Gensburg-Markham Prairie, Goose Lake Prairie, and Illinois Beach State Park. At those locations, caterpillars appear to feed mostly on prairie and bird's foot violets.

The populations of Aphrodite fritillaries and great spangled fritillaries at Illinois Beach State Park in Zion reveal an important aspect of the ecology of both of these species. Great spangled fritillaries can live in more types of habitat than Aphrodites. Therefore, people often see them fluttering throughout most of the park, particularly in the black oak savannas. In contrast, Aphrodites dwell only in the open, wet prairies that occur in the troughs, or swales, between the park's dune ridges. As a consequence, visitors wandering the nature trails are far more likely to encounter great spangled fritillaries than Aphrodites.

The strong dependence of Aphrodites on prairie habitats suggests that these butterflies are one of the species most likely to benefit from prairie restoration. So far, however, this does not seem to have happened. Although the species seems to be thriving under current management on sites where it already flies, Aphrodites are not colonizing new sites that have been restored to prairie. One reason for this might be that the prairie violet species are difficult to restore. The process of gathering seeds from violets requires much time and effort.

Consequently, many sites that have otherwise been restored to vibrant communities lack violets. If land managers can improve techniques for the widespread planting of prairie and bird's foot violets, we may restore these spectacular insects to many additional places in Chicago Wilderness.

—Doug Taron