SCOTT SHALAWAY What's the buzz on yellow jackets?

Festival season seems to peak in October, perhaps because clear skies and mild temperatures are perfect for outdoor activities. But warm fall days can turn apple festivals and Oktoberfests into yellow jacket-infested nightmares. Few of nature's pests are more bothersome than yellow jackets ringing the rim of a cup of cider or a plate of potato salad.
Understanding why yellow jackets get so aggressive in the fall won't make the problem disappear, but at least you won't feel nature's conspiring against you.
Active time: Yellow jackets are active all summer long, yet unless you run over their nesting burrow with the lawn mower, they are rarely aggressive or bothersome. But on warm fall days, they turn maddeningly irritable and prone to sting. The simple explanation is that the social structure of the nest has broken down, and they are hungry.
Let's back up a few months and tell the whole story. Yellow jackets build their nests underground in abandoned rodent burrows. In the spring each colony begins with a single fertilized female or queen. (She mated the previous summer.) The queen begins the nest by chewing woody material to make paper-like material to build the nest.
She begins by building a series of hexagonal cells in which she lays a single egg. At this point the nest resembles the paper wasp nests that appear under the back porch roof. She also begins building an outer shell that envelops the entire nest. A yellow jacket nest is much like the nest of its close kin, the bald faced hornet, except that the yellow jacket nest is built underground while a hornet nest hangs in a tree.
Collects food: After the queen lays her first clutch of eggs, she collects food for the soon-to-hatch larva. Any small insect is fair game, but small fleshy caterpillars are favorite larval foods. She chews the prey with her powerful jaws, then deposits some in the cells with each egg. Upon hatching, the larva eat the awaiting food and grow rapidly.
When the first generation of yellow jackets matures, they continue expanding the size of the nest and collecting food for subsequent generations of larva. The queen then becomes an egg-laying machine and probably never again leaves the nest.
As the colony grows, the workers expand the size of the subterranean burrow. Watch carefully, and you'll see workers leaving the burrow with clumps of soil in their jaws. Throughout the summer, the queen continues to lay eggs, while workers continue to excavate the burrow, enlarge the nest, and feed the larva. The workers also feed the queen and nourish themselves with nectar and pollen.
Breakdown: By late summer, as days become noticeably shorter, the yellow jackets' incredibly sophisticated social system begins to break down. The queen begins laying eggs that develop into both fertile females and males, and those individuals mature and mate. Then the males die, and fertilized females seek refuge for the winter in hollow logs or under thick slabs of bark. When these pregnant queens-to-be emerge in the spring, they disperse, and each builds a new colony of her own.
Meanwhile, the rest of the original colony disperses and dies off. Since the workers no longer have a colony to tend to, they are on their own until they die. On warm fall days they search for nectar and pollen amid a sea of dying wildflowers. With natural foods in short supply, fall festivals provide an almost unlimited menu -- soda, beer, cider, hot dogs, etc. That's why yellow jackets bedevil us so this time of year.
Bald-faced hornet nests also become conspicuous in the fall. As leaves drop from the trees, basketball-sized paper hornet nests become obvious hanging from tree branches.
Hornets are essentially large yellow jackets, and their life cycle mirrors the yellow jacket's, except for where they build their nests. New nests are built every year, so hornet nests are safe to collect and dissect after a prolonged period of subfreezing temperatures. I'd wait until December or January to bring a hornet nest into the house to show the kids, and even then beware that a groggy old queen may have not yet given up the ghost.
sshalaway @aol.com.