Polybiine workers say, “Don’t even think about attacking this fortress.”
As the holiday season draws to an end and the chilly grip of old man winter settles in, it’s time for Bug of the Week to head for warmer realms to visit insects and their kin in tropical places. Over the next several weeks, we will meet relatives of our native Maryland insects enjoying warm weather somewhere else on planet earth.
Here: In late autumn a concerned gardener contacted me about a large paper nest suspended in the leafless branches of a tree near his home. Due to the large size of the recently discovered nest, he was concerned that wasp activity would resume in spring, posing a threat to people and pets. The nest he described was clearly that of the baldfaced hornet, masters and marvels of hymenopteran engineering. The story of the nest begins in spring, when a queen that survives the rigors of winter selects a location to build her nest. Usually the limb of a tree or shrub will do, but I have seen nests beneath overhangs of sheds and houses. The queen gathers wood and plant fibers, chews them into a papery pulp and builds a few brood chambers, into which she places eggs. She then constructs thin papery envelopes to enclose the brood cells that are home to her daughters. Larvae that hatch from the eggs are fed macerated caterpillars, flies, moths, and other insects captured by the queen. These larvae soon develop into workers that assist the queen in gathering food, enlarging the nest, and tending to the needs of their sisters and the queen. As the colony grows, the mother queen spends less time out foraging and more time at home laying eggs. Her daughters shoulder the load of finding dinner for their sisters and mom.
Just inside the opening of the nest, baldfaced hornet workers watch a foolish human with a camera. Should we teach him a lesson or give him a pass?
The rapidly growing nest is in a constant state of transition. Portions of the exterior papery envelope are removed to accommodate an ever expanding number of brood cells. By late summer the colony is in high gear, with hundreds of workers capturing prey and raising young while the queen feverishly lays eggs. By early autumn the nest can reach the size of a small beach ball. As autumn approaches, workers build over-sized brood cells into which the queen deposits egg destined to become new queens and males. The mother queen then dies and the virgin queens fly away and mate before seeking hibernal shelter under bark, inside fallen logs, or in other protected locations. The common misconception that the large paper nest will house hornets for multiple seasons was the source of my friend’s consternation. Before winter, the nest is vacated by workers, queens, and males. Once empty, it will not be used again.
There: About 2000 miles south of Maryland, species of tropical polybiine wasps build paper nests in trees and shrubs throughout the forests. Nests are constructed in a variety of shapes and colors characteristic of different species. However, my experience is that all of these nests are guarded by a phalanx of sometimes colorful but always highly alert workers ready to attack and repel unwanted intruders. Like their temperate zone cousins, tropical wasps use powerful jaws to strip wood fibers from plants and macerate the fibers into pulp. The papery wood pulp is then fashioned into cells of horizontal brood combs and into a papery envelope to enclose the brood and protect the colony from marauding predators and parasites, as well as nasty tropical storms. Polybiine wasps, like their northern kin, are rapacious predators capturing fresh meat in the form of caterpillars, small flies, termites, and other soft bodied insects to feed hungry larvae back at the nest. Unlike colonies of baldfaced hornets where a single monarch rules the nest, many colonies of polybiine wasps have several queens that share the load of producing brood. The seasonal cycle of some polybiine wasps also differs from that of their northern relatives. While nests of baldfaced hornets only last a season, nests of tropical polybiines may last several years. Chilly winters drive colony cycles in the north, and in tropical regions the dry season governs prey availability and colony activity. Irrespective of location, north or south, these fierce paper nest makers are wonders of the insect world and creatures to be observed quietly at a respectable distance.
Under the compound eyes of watchful guards, tropical polybiine workers close a gap in the paper envelope that covers the brood comb.
References
We thank an inquisitive friend for providing the inspiration for this Bug of the Week after discovering a nest of baldfaced hornets near his home. The ever fascinating book “The Insect Societies” by E.O. Wilson was used as a reference for this episode.