Hornets and WaspsSome early leaves are starting to turn on stressed trees, students are trickling back to campus, and it sure was chilly last night. Fall is coming, and we in the landscape department can tell from the gigantic hornet nests appearing seemingly out of nowhere. They’ve probably been there all along, of course, but late summer seems to be when they are seen. It’s a population thing, the hornets have been building nests all summer, but the size of the colony grows all summer, so the later in the summer we get, the larger the nests become as more workers are available for nest building.
We’re talking about two different insects here, Hornets, Dolichovespula maculata (Linnaeus), and Northern Paper Wasps, Polistes fuscatus pallipes Lepeletier, or European Paper Wasps, Polistes dominula. The paper wasps can be identified by the nests with open bottoms, like an upside down umbrella, while the hornets make their paper nests pear shaped and solid looking, with only a hole at the bottom. In case you are curious, the “paper” is ground up plant tissue and wasp spit. And no, I’m not getting close enough to take pictures so you can identify the bees while away from the nest, try Wikipedia.
Both hornets and wasps are beneficial insects, preying on beetles, caterpillars, and flies. Paper wasps are known for preying on Corn Earworm, Tobacco Hornworm, and Armyworm, while hornets enjoy a good meal of flies. All of these are partially eaten, and then fed to their young. The adults feed on nectar, and are considered minor pollinators.
Unlike honeybees, wasps and hornets can sting multiple times. Paper wasps aren’t nearly as aggressive as hornets. In fact, killing a hornet near its nest is a particularly bad idea, as it sends out a pheromone and could cause a swarm to come and attack in defense of the hive.
Only fertilized females overwinter, hiding in cavities in trees, or in the ground. The nests are not used the next year. All the workers (unfertile females) do all the work of feeding and nest building, the males (drones) are born late summer, and hang around to fertilize the eggs, and the fertile females wait for winter to go hide until spring to start the process again. The fertile females and males are not born until late summer, and, as seems appropriate for someone doing no work around the house, the males die after mating. A colony can contain up to 700 insects.
While it would be great to leave all the nests we find on campus, we remove any that may cause even a slight threat to anybody in our community. Many seem to be in lamp posts, and they are also quite fond of the large green electrical boxes near many of our buildings.