Juvenile hormone affects age polyethism, ovarian status, and cuticular hydrocarbon profile in workers of a Polybia occidentalis wasp

Division of labor is one of the most striking features in the evolution of eusociality. Juvenile hormone (JH) mediates reproductive status and aggression among nestmates in primitively eusocial Hymenoptera (species without morphologically distinct castes). In highly social species it has apparently lost its gonadotropic role and primarily regulates the division of labor in the worker caste. Polybia occidentalis, a Neotropical swarm-founding wasp, is an ideal model to understand how JH levels mirror social context and reproductive opportunities because of the absence of a clear morphological caste dimorphism. In this study, we tested the hypothesis that JH influences division of labor, ovary activation and cuticular hydrocarbon profiles of workers. Our observations confirmed that JH analog (methoprene) and precocene affected the cuticular chemical profile associated with the age polyethism. Also, methoprene and precocene-I influenced differently ovarian activation of treated females (individuals treated with methoprene expressed more activated ovaries while precocene treatment did not have significant effect). These results suggest that different hormonal levels induce a differential expression in the cuticular chemical profiles associated with the workers’ age polyethism, which may be essential for keeping the social cohesion among workers throughout their lives in the colony. Furthermore, JH is likely to play a gonadotropic role in P. occidentalis. JH has apparently undergone certain modifications in social Hymenoptera, presenting multifaceted functions in different species.

Opportunistic Strategies for Capture and Storage of Prey of Two Species of Social Wasps of the Genus Polybia Lepeletier (Vespidae, Polistinae, Epiponini)

The foraging activity in social wasps is complex behavior that involves the ability to locate and transport the resources necessary for the colony. The activity is opportunistic and generalist, sometimes adapting to the availability of the resources when the colonies are exposed to critical environmental conditions. The aim of this study was to evaluate the opportunistic behavior of two species of wasps of the genus Polybia for the capture and storage of prey in the form of flights of winged. Five colonies of Polybia occidentalis (Olivier) and two colonies of Polybia paulista (L.) were collected. Six of them contained stored winged of termites, and one contained winged of ants. The results indicated that these two species practice an opportunistic foraging strategy and are able to store large quantities of protein resources in their colonies.

Polybia (Myrapetra) scutellaris (Hymenoptera: Vespidae) foraging on flies at carcasses of Rattus norvegicus (Rodentia: Muridae)

Social wasps stand out due to their role in the trophic balance of the ecosystems. These insects can get nutrients by preying on other insects, such as Lepidoptera, Diptera, Hymenoptera and the decomposing remains of vertebrates. Some species, such as Polybia scutellaris, can also use pollen and nectar stored in their nests to produce honey. Some studies lay emphasis on the prey captured by social wasps, showing that predation, in some conditions, is directed to Lepidoptera larvae, such as for Polybia occidentalis, Polybia paulista and Polybia ignobilis. Other species like P. scutellaris focus on flies of the Tabanidae, Syrphidae, Muscidae and Anthomyiidae families. There are few studies with social wasps that feed on animal carcasses; this way, our study aims to report the predation on individuals of the Sarcophagidae family, which use Rattus norvegicus carcasses as a food source, by the social wasp Polybia scutellari

Cue-Mediated Recruitment in a Swarm-Founding Wasp: Successful Foragers Induce Nestmates to Search Off Nest for a Scented Carbohydrate Resource

The ability of social insect colonies to recruit nestmates to profitable resources increases colony-wide foraging efficiency by providing individuals with information that narrows their search for resources. Here we ask if for the Neotropical swarm-founding waspPolybia occidentalisnaïve nestmates are able to use food-scent cues from rich carbohydrate resources brought to the nest by successful foragers to orient to off nest resources. Foragers were allowed to freely visit a training dish containing a scented sucrose solution. At a second location, in a different direction from the nest, two sucrose-filled dishes were offered, one with the training scent and one with an alternate scent. Naïve foragers preferentially chose the training scent over the alternate scent, indicating that natural rates of resource inflow to the nest are sufficient to induce nestmates to forage at resources with a specific scent. Naïve foragers did not forage more often at the location at which the active foragers were foraging, an indication that directional information is not communicated in this species. The total number of foraging trips made by a colony's foragers was not determined by the size of the foraging force, but rather by the average individual foraging rate for the colony.