Polistes biglumis is a species of social wasp within Polistes, the most common genus of paper wasp. It is distinguished mainly by its tendency to reside in montane climates in meadows or alpine areas. Selection pressure from the wasp's environment has led to several idiosyncrasies of its behavior and lifecycle with respect to its relative species in the genus Polistes. It alone among paper wasps is often polyandrous. In addition, it has a truncated nesting season that gives rise to unique competitive dynamics among females of the species. P. biglumis wasps use an odor-based recognition system that is the basis for all wasp-to-wasp interaction of the species. The wasp's lifecycle is highly intertwined with that of Polistes atrimandibularis, an obligate social parasite wasp that frequently invades the combs of P. biglumis wasps.
Taxonomy and phylogeny
Swedish zoologist Carl Linnaeus described Polistes biglumis in 1758. Its species name biglumis is a Latin phrase meaning "two husks." While no common name for the wasp exists in English, it is referred to as berg Feldwespe in German (meaning "mountain field wasp"). P. biglumis has been studied alongside Polistes snelleni and Polistes chinensis for comparison. P. biglumis was originally classified as a hornet in the genus Vespa, but was reassigned to the genus Polistes, which is the largest genus of paper wasps in the family Vespidae.
This species resides mainly in mountainous zones in Southern Europe, and it is the only paper wasp that inhabits a mountainous clime. Due to its divergence from the more common temperate climes of its genus, it has developed several distinctions from other paper wasps that arise mainly from selective pressure due to the severe climate it commonly experiences. The climate shortens the nesting season of P. biglumis to around four months. In addition, the nests exhibit darker coloration, which allows them to absorb more heat from the sun. Workers are also often nonexistent in some populations of P. biglumis, which demonstrates a large dichotomy from other social wasps, whose most commonly seen specimens are the workers. Finally, because of the reduced nesting season and parasitism by other wasps, P. biglumis has developed nesting strategies that are both distinct from other paper wasps and variable among conspecific populations.
Subspecies
P. b. alpium Blüthgen, 1957
P. b. biglumis (Linnaeus, 1758) P. b. bimaculatus (Geoffroy, 1785)
Description and identification
Polistes biglumis can reach a length of up to (queen), (workers), (males). It is a larger species of wasp in comparison to its relatives in Polistes. It also exhibits darker coloration compared to other paper wasps; it has a black petiole for both sexes. The females exhibit black abdomens, as well, with rare yellow spots. Males, however, have largely yellow abdomens. Adult wasps can be distinguished from the young because they are darkly colored and can fly, whereas young wasps have paler stripes and are flightless.
Workers and queens do not exhibit morphological differences, but they can be distinguished physically by the abundance of their fat layers and behaviorally through their relative foraging efforts. Queens have more abundant fat layers and are also significantly less likely to participate in foraging for the nest. In addition, the color of the fat layers is distinct for workers versus queens; the workers exhibited yellow fat layers while the queens exhibited milky fat layers.
The nests of P. biglumis are circular or elliptical in shape and are hung vertically by one pedicel. They are largely produced by the foundress during the phases of egg and larval production. The peripheral cells are generally uninhabited. Nests are more likely to be closer to the ground versus other Polistes wasps because the ground offers thermal inertia and shelter from strong winds. The nest material is also key to nestmate recognition because nest surfaces are impregnated with the epicuticular hydrocarbons that establish the framework by which the individuals discriminate between other wasps.