Last summer, we had a colony of bald-faced hornets (Dolichovespula maculata) take up residence on our back deck.
We’re weirdos who are quite fond of insects. Usually, we’re more than happy to have predatory insects around to help us manage populations of pest insects in our organic garden — paper wasps, mantids, ladybugs, lacewing larvae, wheelbugs, Florida predatory stink bugs… our gardens are chock full of both predator and prey insects.
View this post on Instagram
We see this every year, but it’s always amazing… This large green worm is a tobacco #hornworm, the larvae of the beautiful Carolina sphinx moth. They’re common pests that eat tomato and other nightshade plants (this one was on an Incan golden berry leaf). They’re one of our ducks favorite foods but they’re also a host for the larvae of beneficial predatory parasitoid wasps. The white spots sticking off of the green hornworm are the cocoons of metamorphosing parasitoid wasps. The parent wasps paralyzed the hornworm, laid eggs inside of it, and its larvae made a meal of the worm before forming the tiny white cocoons on its surface, out of which mature parasitoid wasps will soon emerge. Once the tiny adult wasps emerge from the cocoons the predator > prey cycle will start anew. How were our parasitoid wasps able to find the well-camouflaged tobacco hornworm hidden amongst all the leaves? The plant “told” the wasps where to look. As the herbivorous hornworm starts to chew on the leaves, the worm used a chemical called volicitin in its saliva to soften the tissue of the plant. A plant can’t run away, swat at the hornworm or scream for help, but it is anything but defenseless. When the plant’s immune system detects volicitin, a chemical “conversation” begins, although it’s not in the same language that people speak. Instead of crying “help!” the plant began releasing a set of airborne semiochemical compounds to alert predatory insects that there was a meal waiting for them, while at the same time alerting other nightshade plants in the area that a hornworm attack was underway. As a result, the parasitoid wasps were able to easily find their target and other nearby plants in our garden responded to the plant’s warning by boosting their own natural pest-repelling and insecticidal compounds to help them fend off a potential attack. Ecosystems are communities whose members thrive through collaboration, not just competition. Unfortunately for this hornworm, it happened to find itself in a well-guarded, interconnected community. #ecosystem #integratedpestmanagement
However, in the case of bald-faced hornets taking up residence on our back deck, we were a bit nervous. For one, we spend a good bit of time on our back deck, as does Bob the Cat. Bald-faced hornets (which are “aerial yellowjacket” wasps, not true hornets) have a ferocious reputation. Reports of them stinging people abound.
Did we really want 500+ worker hornets in our living space? Continue Reading