What wasps do behind closed doors.

What wasps do behind closed doors

"For a long time entomologists have been interested in the nocturnal activities and sleep of social insects," says Manfred G. Walzl of the University literature as early as 1916.

Recently, with the help of modern technology, Walzl managed to get the lowdown on hornet nightlife. He used an infrared viewing device to make continuous, nightly observations of two separate hornet nests between 5 p.m. and 4 a.m. -- recording on videotape much of what he saw. He went so far as to remove a segment of one nest's outer wall and cover it with a piece fo transparent plastic. What he saw wouldn't make a social animal blush, but it answers some of old questions.

With mating restricted to a single, fertile queen, it seems there's not much to do but sleep. Come bedtime (10:00 p.m. at the latest, Walzl observed), each hornet crawls head and shoulders into a small, horizontal cell, where it spends the night with its abdomen hanging out. During darkness the nests are not guarded continuously, as they are in the day, but every 20 minutes to 1 hour several workers come out to inspect the outside of the nest. While sleeping, hornets experience "reduced ventilatory pumping" (their breathing slows) until it's time to get up. The first worker sleave at 4:00 a.m.

Nobody knows if hornets are afraid of the dark, but Walzl's observations and light-meter measurements suggest some lack of nocturnal aeronautical acumen. When the hornets came home for the evening, he found, "With light above 1 lux [a little brighter than moonlight], the hornets reached the nest directly in flight. Below 1 lux the nest was approached by walking."