Social Wasps 101

What does it mean to be social? Being social, or sociality, is defined as a group of individuals of the same species exchanging information and cooperating in one way or another. The key to this cooperative living is communication. The word communication is derived from the Latin word “communis,” which is translated to mean “to exchange or share obligations.” That is precisely what these social insects do: they share information on where to eat, what to eat, dangers to avoid, potential mates, etc. Many interactions in the insect community demonstrate characteristics of sociality; however, not all insect gatherings are considered “social.” Many times, a large gathering of insects indicates a response to an environmental stimulus, either positive or negative. There are numerous forms of social behavior among insects: eusocial, semisocial, subsocial, solitary, communal and quasisocial.

So then, what makes an insect truly social? To be considered eusocial (truly social), an insect species must exhibit cooperative care, reproductive division of labor, and an overlap of generations. Insects demonstrate cooperative care when all members of a colony collectively take care of the brood. Division of labor means that some members of a colony will mate and reproduce while others will never be given the opportunity. Finally, overlapping generations occur when certain offspring grow up to help parents feed and nurture their young. The two orders of insects that contain eusocial species are Hymenoptera (ants, bees and wasps) and Blattodea (termites).

Social behavior in insects is not limited to eusociality, though. Insects that demonstrate other degrees of sociality may exhibit some, but not all, of the three characteristics discussed above. For example, subsocial insects do not exhibit all of these behaviors, but adult subsocial insects will care for their young to a degree. Common species of insects characterized as subsocial include cockroaches, true bugs, aphids, and earwigs. Some species of solitary insects, such as butterflies, although not social, will aggregate together.

There are many benefits to group living. One of the primary benefits is strength in numbers. Animals that live in groups and communicate together have an increased likelihood of survival. They have more eyes available to watch for predators as well as chemical communication through pheromones. These pheromones produce an odor that can alert the rest of the colony to oncoming danger. Another benefit to living in numbers is related directly to survival. It is less likely that a predator will single out any one individual, and typically when a predator reaches a colony they will soon realize the danger of large numbers. Two other benefits of group living are the increased success of raising young and increased likelihood that an individual will find food. One of the characteristics of being social is cooperative care of young. There are numerous individuals whose only job is caring for the young. This fact alone increases survival rates, as many hands (or tarsal claws) make light work. Finally, because colonies consist of such large numbers, there are always several individuals foraging for food. This increases the likelihood that the entire colony will be fed or know where food sources are located.

Photo credit: Gene White

PMPs & SOCIAL INSECTS. There are a number of social insects that pest management professionals may encounter, including several different types of wasps (some are social and some are not). For example, we often come across cicada killers or cuckoo wasps. Most of the time, these solitary wasps are not aggressive and positively impact their environments as pollinators. However, the wasps that we must be most concerned with are social. There are about 20 species of social wasps in North America and more than 700 social wasp species worldwide. These wasps are in the family Vespidae and typically fall into three groups: yellowjackets, hornets and common paper wasps. Yellowjackets and hornets are in the genuses Vespula and Dolichovespula spp.

Yellowjackets and hornets present constant problems around residential areas. They are a medium-sized wasp that is black with patterned bands of bright yellow or white, the latter of which can be seen in Dolichovespula maculata, commonly known as the bald-faced hornet. Yellowjackets and hornets can be distinguished by their coloration and nesting. Yellowjackets typically build their nest in underground cavities, while hornet nests are always located above ground. Because yellowjackets make nests underground, detecting their nesting sites is challenging — their presence often goes unnoticed until someone steps on or otherwise disturbs a nest. Yellowjackets often nest in rodent burrows or low-lying wall voids where they can remain hidden.

Bald-faced hornets, on the other hand, always build their large, football-shaped nests above ground. Both wasp species surround their nest with paper walls to protect against weather and natural enemies. Both yellowjackets and hornets are aggressive and will readily sting, especially when their nests are threatened. When threatened, they emit an “alarm pheromone” which alerts the colony of pending danger. This results in an aggressive attack from the rest of the colony. These wasps are readily attracted to sugar sources, such as berries and flower nectars. When sweet sodas and ripened fruit are on the menu, they may become unwelcome picnic guests due to their “sweet tooth.”

Paper wasps are the other group of Vespid wasp that are typically dealt with by PMPs. These wasps are in the genus Polistes spp. and are named for the papery nests that queens build and colonies live in. They are long, slender wasps characterized by brownish-reddish colors with yellow markings. Using saliva and wood tissues, paper wasps build their nests facing the ground and attach them to tree hollows or structures, such as the eaves of homes, with a small pedicel. These wasps are not very aggressive and will only sting when threatened.

Wasps are a nuisance around homes, during picnics, and in the workplace. Notably, their sting can pose a double threat: in addition to the pain, many people are allergic to stings. Because of these threats, safe and timely control of these pests is a must. Being aware of these pests’ behaviors better equips us to handle this daunting task.

Kristen Stevens is a corporate entomologist at Cook’s Pest Control, Decatur, Ala.