SCOTT SHALAWAY Yellow jackets: nasty for a reason

A warm fall day brings out the worst in yellow jackets. Just ask anyone who's been to an outdoor fall festival. A belligerent yellow jacket in a cup of cider can ruin an otherwise perfect day. But there's a simple reason these familiar wasps turn nasty in the fall -- they're hungry.
Yellow jackets are active all summer long, yet unless you run over their nesting burrow with the lawn mower, they're rarely aggressive. But on warm fall days, they get mean. The simple explanation is that the social structure of the colony breaks down, and there's not much to eat.
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 a paperlike substance to build the nest. She builds 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.
Food for first batch
After the queen lays her first clutch of eggs, she collects food for the soon-to-hatch larvae. 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 larvae 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 larvae. 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.
By late summer, as days grow shorter, the yellow jackets' 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.
Fate of the rest
Meanwhile, the rest of the original colony disperses and dies. 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 seas 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 hornet nests become obvious hanging from tree branches. Just a few days ago my daughter, Emma, found the biggest hornet nest I've ever seen. It was twice the size of a basketball.
Hornets are essentially large yellow jackets, and their life cycle mirrors the yellow jacket's, except 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 individual may have not yet given up the ghosts.
sshalaway@aol.com