Yellowjacket larvae pay their babysitters in sugar
Adult yellowjackets live mostly on sugar, yet they spend summer hunting insects to chew up for their grubs. In return the larvae ooze a sweet liquid the workers drink. When prey runs short in late summer, that payment dries up, and the wasps start raiding picnics and bins instead.
Yellowjacket is the North American name for social wasps in the genera Vespula and Dolichovespula; elsewhere in the English-speaking world they are simply wasps. Most wear black and yellow, though the bald-faced hornet, despite its name, is an ivory-and-black yellowjacket rather than a true hornet. Workers measure about 12 mm and queens about 19 mm. Unlike honey bees, they lack a dense hairy coat and pollen-carrying hind legs. Every female can sting, and the lightly barbed stinger usually allows repeated stings; the venom is chiefly dangerous to allergic people or those stung many times.
Colonies usually last one year. Only mated queens survive winter, tucked into logs, bark or soil. In late spring a queen builds a small paper nest from chewed wood fibre, lays eggs in 30 to 50 cells and feeds the larvae herself for about 18 to 20 days. Those first offspring become sterile female workers, who take over foraging, building and defence while the queen stays inside laying. By late summer a nest may hold 4,000 to 5,000 workers in 10,000 to 15,000 cells, often reaching basketball size. New queens and males are then reared, leave to mate, and the old colony dies off.
Where winters are mild, as in parts of Australia, New Zealand and the southern United States, nests can survive and swell to enormous size with several laying queens. The southern yellowjacket can build perennial colonies with tens of thousands of workers. Two European species, the German wasp and the common wasp, have spread far beyond Europe and now thrive as invaders in New Zealand, South America, eastern Australia and the south of Africa.
Their hunting has real value. Many of the insects fed to larvae are crop pests. A DNA study of 554 larvae from 14 nests across southern England, within the wasps' native range, found prey from 12 orders of arthropods, marking them as broad generalist predators. So many other insects copy their colouring, from harmless flies and moths to other stinging wasps, that the yellowjacket pattern works as a widely recognised warning.
Source: Yellowjacket
