Polistes fuscatus

Figure 2 (left): P. fuscatus nest. Source: discoverlife.org

Figure 3 (right): Nest made by P. dominula in lab conditions using construction paper. Source: Photo by Jessica Riojas

Lifespan and Reproduction

Average lifespan of P. fuscatus is the time it takes a queen to develop and mate; this is generally about 1 year. Larvae are laid during the late summer and are fed by workers, and these larvae are potentially capable of becoming new queens. These eggs hatch before the fall and the offspring hibernate during the winter within the bark of trees. New eggs emerge in the spring to begin nests and lay eggs. By fall, after laying eggs that will develop into new queens, these queens will die. All accompanying workers and males (Figure 4) die with the queen.

Figure 4: P. fuscatus male. Source: flickr.com/photos/Pingyeh

Food Sources and Ecosystem Roles

P. fuscatus adults feed on plant nectar. In doing so, they transfer pollen from one plant to another, therefore aiding in pollination. Adults also kill caterpillars and other small insects to provide food for their larvae. The wasp will then chew up the insect, absorb the liquid, and regurgitate the solid portion of the food to older larvae and liquid portion to younger larvae. Because it is an insectivore, the wasp plays a large role in large-scale pest control.

Social Hierarchy

P. fuscatus is a social species with complex societies based around a single queen. One fertile female begins building a nest after winter hibernation. Other fertile females may begin working with her in multiple foundress situations, but the original female is considered dominant. Once the nest is built, the co-foundresses are either driven away or demoted to a worker status. These secondary females may still be fertile, but the queen will eat the eggs to assert her dominance. The first offspring produced by the queen are infertile females who become the “true workers.” The queen will lay eggs in the late summer that are capable of becoming fertile females. In Polistes, the social system consists of workers that are based on a hierarchy system under the queen’s rule.

The role of the queen is essentially a central pacemaker and coordinator of colony activity. The queens spends the most time on the nest, spends more of its nest time active, and participates in and initiates more interactions than the active worker. Removal of the queen decreases worker activity levels and causes worker activity to become less synchronized. However, presence of an inactive queen on the nest causes an even greater reduction in worker activity level and worker synchronization than in the absent queen situation. Removal of a worker has no effect in the nest activity or on other colony workers.

Facial Recognition

Figure 5: Various faces of nine female P. fuscatus. Source: Tibbetts Lab.

Individual recognition is essential in interactions in complex social systems. In P. fuscatus, a linear dominance hierarchy is established to determine how food, work, and reproduction are divided in the colony. In order for this hierarchy to be stable, individuals of different ranks must have some degree of recognition.

P. fuscatus have individual variance in their yellow facial and abdominal markings (Figure 5). In a facial recognition study, wasps whose yellow markings are experimentally altered with paint received more aggression than control wasps who are painted in a way that does not alter their markings. Aggression declines towards wasps with experimentally altered markings as these novel markings become familiar. The evolution of facial recognition in wasps is associated with specialized face-learning abilities. P. fuscatus can distinguish among normal wasp face images better than non-face images or manipulated faces (Figure 6). P. fuscatus learned to distinguish between faces better than between patterns, caterpillars, antennae-less faces, and re-arranged faces (Figure 6 & 7).

Figure 5: (A) Polistes fuscatus made more correct choices when trained to discriminate between pairs of face images rather than patterns or caterpillars.

(B) Polistes fuscatus made more correct choices when trained to discriminate between pairs of face images rather than manipulated faces.

Source: Tibbetts and Sheehan (2013)