Once again it’s time to escape winter’s chill and head to the rainforest to see what’s up in the world of nocturnal arthropods. For the past two weeks we embarked on an 1800 mile journey to the forests of Costa Rica to observe spooky whip spiders and cryptic katydids. This week near the hamlet Santo Domingo, under the light of a full moon, we visit a marvelous nest of polybiine paper wasps constructed beneath the frond of a palm tree. Polybiine wasps build paper nests in trees and shrubs throughout the forests of Central America. 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 female workers ready to attack and repel unwanted intruders.
Even a gentle rustle is enough to trigger the alarm and send a squadron of wasps to the exterior of the nest ready to attack.
Like their temperate cousins European hornets and baldfaced hornets, 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. A papery envelope is built to enclose the brood and protect the colony from marauding predators and parasites and nasty tropical storms. Polybiine wasps 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.
Beneath the glare of a flashlight, the nightshift of nocturnal polybiine workers feverishly toils to enclose fresh comb within the nest. By evening the next day the paper envelope is almost complete.
Unlike colonies of many of our temperate wasps where a single monarch rules the nest, colonies of polybiine wasps may have several queens that share the load of producing brood. Within the colony of some polybiine wasps the work of the colony is divvied out based on the size and age of the workers in a phenomenon known as polyethism. Clever scientists discovered that small workers tend to be dominant to large rapidly developing workers in the polybiine wasp Polybia occidentalis. Large subordinate workers took up dangerous out of the nest tasks of gathering food and finding construction materials for the colony. Smaller workers were more likely to stay at home and perform important tasks within the nest.
The seasonal cycle of some polybiine wasps also differs from that of their northern relatives like baldfaced hornets. While nests of baldfaced hornets only last a season, nests of tropical polybiines may last several years. These long-lived colonies may contain thousands of workers. Chilly winters drive colony cycles in places like Maryland, but in tropical regions the patterns of rainfall, seasons of wet and dry, govern 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.
We thank the hospitable hosts of the Rafifki lodge for providing the inspiration for this Bug of the Week. The ever fascinating book “The Insect Societies” by E.O. Wilson, and the stimulating article “The Roles of Body Size and Dominance in Division of Labor Among Workers of the Eusocial Wasp Polybia occidentalis (Olivier) (Hymenoptera: Vespidae) “ by S. O'Donnell and R. L. Jeanne, were used as a references for this episode.