My friend, John Howard, captured this photo of the miniature beasts. They almost look like little fairies. When you encounter a large group of them on a stem, the whole plant appears to be moving. There are many different species of woolly aphids, all specific to the plants they dine on, and many are considered pests.
Then enters the predator, the Harverster butterfly, Feniseca tarquinius. Oh, it looks innocent enough. They even have a sweet look about them, with their little upturned "nose". The adults are fairly friendly, sometimes lighting on ones finger. I was able to get really close to this one before it decided to fly away. Adults will hang around woolly aphid colonies and lay their eggs amongst the aphids.
When the caterpillars hatch, they ruthlessly snack on the aphids. The scientific name, Feniseca tarquinius, alludes to this behavior. Feniseca means "harvester" and Tarquinius was an evil king who ruled in Rome from 534 to 510 BC and was expelled for his cruelty. Ah, I love scientific names! Here is a picture of the "cruel harvester" from Bugguide. The Harvester is the only known carnivorous butterfly caterpillar in the United States.
Some of the Harvester caterpillars will cover themselves with the carcasses of the woolly aphids they have eaten. They attach the bodies to them with caterpillar silk. The aphids woolly exterior makes them distasteful to most predators, and protects the caterpillar from its enemies. It also works to fool the ants that guard the aphids and keeps the caterpillar from being attacked. Many different species of ants will guard aphids. They protect them in exchange for honeydew, a sweet substance the aphids produce from the plant juices they consume. The ants will stroke the aphids with their antennae and the aphids will release the honeydew. If anything threatens the plant the aphids are on, the ants will come running to bite the would be intruder.
The adult Harvester has a short proboscis, so it cannot reach the nectar in flowers. Instead they feed on aphid honeydew, dung, carrion and mud. Because of this, Harvesters are rarely seen. We do have records of them here in Indianapolis, so keep your eyes peeled and you might be delighted to see this beauty with the interesting life-cycle.