Spring Azures spent the winter as pupa, cozy in their chrysalises, poised to take the final step to adulthood when spring conditions were right, with longer days and warmer temperatures. Their fluttering flight showing flashes of azure began lighting up woodlands and gardens earlier than usual this year, when unseasonably warm March temperatures encouraged them to complete their metamorphosis and emerge as early as the last week of March.
Nectar was scarce in those early days of emergence, especially when weather whiplash sent the temperatures in the opposite direction, dropping below normal. During the lean times, Spring Azures got their nourishment from a variety of mineral sources, including mud puddles, rocks, leaves, and even bird droppings.
As temperatures soared again, nectar supplies became plentiful.
Now their priority is reproduction – making sure their species has a future. After mating, female Spring Azures look for plants appropriate for egg-laying, plants whose leaves their caterpillars can eat and on which they will thrive. Spring Azures evolved to use the newly emerging leaves, flowers and buds of a variety of woody plants as their caterpillars’ food, including viburnums, dogwoods (Cornus species), and New Jersey Tea (Ceanothus americanus). For the past week, I’ve watched Spring Azures flitting from plant to plant, and from leaf to bud of Maple-leaf Viburnum (Viburnum acerifolium), taking only seconds to lay each egg.
The eggs will hatch and caterpillars will emerge, nibbling on the newly developing leaves and buds. Not all of the caterpillars will complete metamorphosis to fly as butterflies, however. Caterpillars are very vulnerable to predators, including other insects, spiders and birds. Caterpillars are an essential source of food for birds, especially when they are feeding their young. It may take thousands of caterpillars to feed a hungry clutch of growing birds.
Normally, ants would be among the insects that would love to eat a tasty caterpillar treat. Even when fully grown Azure caterpillars are small, the perfect snack size for an industrious ant on the hunt. To protect themselves, Azure butterflies have developed a way to enlist the ants to protect them rather than eat them. Azures produce delicious honeydew that ants love. The ants guard the Azure caterpillars, palpating them to trigger the honeydew payment.
Ants will work for the highest bidder, and in this case they help some of those caterpillars live to become butterflies.
Cech, Rick; Tudor, Guy. Butterflies of the East Coast. 2005.