Eastern yellowjacket
The eastern yellowjacket or eastern yellow jacket is a wasp found in eastern North America. Although most of their nests are subterranean, they are often considered a pest due to their nesting in recreational areas and buildings. This yellow jacket is a social insect, living in colonies of hundreds to thousands of individuals. Along with their subfamily, Vespinae, this species demonstrates supportive parental care for offspring, separation of reproductive and sterile castes, and overlapping generations. They aggressively defend their hives from threats and are known to inflict painful stings.
Taxonomy and phylogenetics
V. maculifrons, in the family Vespidae and the subfamily Vespinae, is commonly found throughout the Northern Hemisphere as part of the yellowjackets. For example, V. maculifrons is commonly called the eastern yellowjacket and has the black and yellow color that distinguishes the yellowjackets. The specific name maculifrons is derived from the Latin word macula, which means spot, and frons, which means forehead. This refers to the spots on the head of species, which are another distinguishing characteristic. Like other Vespula species, V. maculifrons is a social wasp, so participates in cooperative brood care and division between reproductive and nonreproductive groups.Description and identification
V. maculifrons can be differentiated from other wasp species due to its smaller size and abdominal pattern. The most recognizable features of V. maculifrons are the black and yellow lines on the head, thorax, and abdomen. While the body is curved and wider than the head, the abdomen narrows at its attachment to the thorax, which is thinner than the abdomen. The lines on the abdomen also differ based on caste, with the queens having one flared black line nearest the thorax followed by thinner black lines. Queens also have two black dots between each black line. Individuals of this species range in size from. and weigh roughly. The queens are the largest, followed by the males, and then the workers.A V. maculifrons nest can range from in diameter, allowing for hundreds to thousands of workers inside. A large nest can contain 10,000 to 15,000 cells, with a little less than a third of them dedicated to the larger queen cells. The envelope of the nest is tan-brown to red-orange in color. It is constructed out of worn, decaying wood, which results in a fragile structure. These nests are typically subterranean, but have been found in various sites above ground, including buildings.
Distribution and habitat
V. maculifrons is commonly found throughout eastern North America, extending as far as the Great Plains. In most areas where it is found, it is the most common yellowjacket species. In the spring, the queen selects where to locate the colony. Their subterranean nests are not deep, usually covered by less than of soil. However, nests have been found at depths ranging from just under the surface to deep. These nests are found in hardwood forests and on creek banks, as well as in urban and suburban areas. Within these areas, nests are typically built in sheltered places, which can include underground areas, tree stumps, and attics. Their nests are so frequently found in recreational and residential areas that they are considered a pest.The queen begins constructing and the initial structure of the nest by chewing wood and adding in saliva to make a quick-drying pulp to assemble the paper nest with. The first part of the nest constructed is the stalk, which eventually narrows into a cord before expanding again to form the first hexagonal cell. Other cells are then added to the sides of this first cell and an envelope is built around this first group of cells to form a miniature comb. The queen lays eggs in these cells and, once hatched, these become workers. As soon as these workers emerge, the nest begins to enlarge rapidly.
As more cells are added, the comb grows quickly, and once there are enough cells on the first comb, a second comb is added, and so on. To make room for more cells, the inner layers of the envelope are re-chewed and used to create additional layers outside the nest. As most nests are underground, the cavity is enlarged by removing and dropping soil outside the nest.
Venom
Vespulakinins were first discovered in V. maculifrons. Yoshida et al 1976 discovered several of these bradykinin-like peptides including vespulakinin 1 and vespulakinin 2. They and the entire vespulakinin family are insecticidal and may prove useful for human purpose.Hymenoptera, the order to which V. maculifrons belongs, is the leading cause of anaphylaxis in humans. Reactions are usually triggered by proteins in the venom.
Colony cycle
A colony consists of three types of individuals in a social group - queens, workers, and males. New colonies are founded annually during the spring. This is determined by location, but typically occurs around May or June in the northern regions and around September in southern regions. Due to the seasonal differences, the northern cycle is typically shorter than in the south, resulting in smaller nest sizes. A queen, which mated earlier in the year and spent the winter in diapause, founds a colony by raising the first group of workers. Until the first offspring emerge as adults, the lone queen lays eggs, forages for food, cares for the young, and defends the nest. These workers maintain and expand the nest when they mature, while the queen continues to produce more offspring. The workers' job is to build 850 to 9700 cells, of which about 30% are dedicated to queen cells. When these queen cells begin to be constructed, the nest is said to have matured. In the north, colonies peak around August or September, while southern colonies tend to peak around October to November. When winter comes, the colony dies and only some of the queens survive to begin a new colony the next nesting cycle.Behavior
Communication
For V. maculifrons workers to communicate with others in the nest about a potential predator, they have an alarm pheromone that stimulates defense. This pheromone is linked to the sting apparatus and prompts attraction and attack. When the alarm pheromone is expressed, wasps around the nest entrance are typically seen circling, outlining a zigzagging flight, and going directly towards the target. However, foragers that were not at the nest when the pheromone was expressed do not respond in a similar manner. The facultative social parasite of V. maculifrons, Vespula squamosa, responds to the alarm response of V. maculifrons, suggesting common chemistry between pheromones. Since V. squamosa is known to take over nests of V. maculifrons, selection for V. squamosa favors the ability to recognize and respond to alarm calls within the nest.Mating behavior
Male/male interactions
Males of V. maculifrons tend to form loose aggregations, resembling leks, during mating. In one area, hundreds to thousands of males patrol prominent trees and bushes by constantly flying around them. Males typically patrol large areas randomly, rather than limiting to a few trees. If a male sees a female while patrolling, he flies closer to the female in a zigzag fashion and stops on a nearby leaf. This then allows the male to climb onto the female's gaster from behind. Other males do not try to approach an ongoing copulation, but a male might try to copulate immediately after. If a second mating occurs, sperm competition may favor the second male. As a result, males can prevent competition from another male by elongating copulation.Female/male interactions
A queen can mate 48 hours after emerging from the pupal stage. To find a male, queens fly to trees and bushes where males gather in groups. Males frequently groom their legs, antennae, and gasters throughout courtship, mating, and after contact with a queen. The queens have also been seen to groom the face and antennae, but only briefly. At the end of copulation, a queen is able to produce an olfactory or contact pheromone to signal release to the male. The queen also begins to nibble the dorsal surface of the male's gaster to further signal the end of copulation.Since both queens and males can mate multiple times, it is advantageous for the queen to signal when her spermatheca is full, thereby preventing the waste of resources and time. Having strong genital locks for mating is also advantageous for males due to male-male competition, but it can cause problems during disengagement. In the laboratory, both females and males have died during disengagement, sometimes leaving reproductive parts attached to the opposite sex.