By late summer, most of us have been pestered by yellowjackets at picnics, and some of us noticed the gray, football-sized paper nests of bald-faced hornets attached to twigs in trees.

I have seen an occasional yellowjacket tussling with a fly on a flower. And many of us are afraid of these bee-sized members of the yellowjacket wasp family because they deliver painful stings if threatened or if their nests of larvae are in jeopardy.

These wasps are not hornets. We just call them that. Yellowjackets are yellow and black barred, while bald-faced hornets are black with white markings, especially on their faces.

These related wasp species, which live across much of the United States, have characteristics in common, demonstrating their relatedness. Both kinds live in colonies, each community having a fertile, egg-laying queen; many sterile female workers; and a few males late in summer.

Workers chew dead wood into pulp to make six-sided paper cells that house larval wasps until they mature. Workers catch and paralyze insects, tear them apart, and feed them to the larvae in their paper cells in each paper nest. Workers consume flower nectar themselves and feed it to males and the queen. The males’ only job is to mate with the new queen of the year.

In spring, young queens of both species emerge from the soil they wintered in. Each queen of both kinds scrapes dead wood off trees and wooden products, chews it to a pulp, and makes a small, paper nursery with a few six-sided cells inside.

Yellowjacket queens make their homes in the ground with a small entrance to the surface, while bald-faced hornet queens build theirs in trees, with a small hole in the bottom of the nest. Each queen lays fertile eggs and tends the first brood of larvae of the year herself, feeding them paralyzed insects.

That first brood of the year, when mature, and succeeding broods of sterile females, work together in harmony. They continue adding more paper cells, and more layers of paper protection against weather and predators, such as some birds and insects, around that mass of cells all summer. The queen’s only job then is to lay eggs. But her reign of laying is for one summer.

As their populations and paper nurseries grow, one can see worker females constantly going to and coming from the entrances to their nests. Those workers are foraging for nectar for themselves, the males, and the queen of each colony and for insects to feed to the larvae in paper cells in that community.

Late in summer, a new queen matures in each paper community and is fertilized by one of the males in that colony. In the chill of autumn, old queens, workers, and males leave their paper homes and die.

Only the new queens burrow into the protective ground to survive the winter. New queens are the only individuals to carry the genetic code of their respective species from one year to the next. They alone survive winter and emerge the next spring to start new colonies of female workers and males in new paper nurseries.

This month and into fall, watch for yellowjackets around flowers and picnics, partly for your own protection, and look for the attractive and interesting paper nests of bald-faced hornets hanging picturesquely in trees. Those nurseries, however, are more obvious in winter when tree foliage is on the ground.     


Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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