Parachartergus fraternus

Parachartergus fraternus is a neotropical, swarm founding, polistine wasp species that is distributed throughout Central and South America. They live in nests in second growth tropical dry forests, near pasture fields, roadside areas, and urban areas as well. These wasps eat insects, such as caterpillars of Lepidoptera. They also drink nectar, honeydew, and water. The workers capture their prey during foraging. They also use venom to paralyze their prey in order to consume it later. P. fraternus wasps are not very aggressive and they do not attack when the nest is approached. Parachartergus fraternus is closely related to the species Parachartergus apicalis. These wasps belong to the genus Parachartergus, which has sixteen species distributed from Mexico to southern Argentina. Ten of these species are found in Brazil and two are endemic. Most Parachartergus species have few morphological differences between castes in all stages of the colony cycle. For a wasp species, Parachartergus fraternus is average in size. A typical Parachartergus fraternus forager is about 11 mm long, 3 mm wide across its thorax, and weighs about 0.05 g. Queens do not differ morphologically from workers and are therefore similar in size. The dorsal and ventral parts of the body are blackish which is a characteristic of this species. The abdomen has a fusiform shape with short hairs that can only be seen with a microscope. The abdomen is linked to the thorax by a pedunculum. At rest, the wings are longitudinally bent with the last distal part being clear and colorless (almost white). The wings also have very pronounced veins. The eyes of the wasp are big and compound with a large number of facets. The antennae are bent at a sharp angle and the mouthparts are orange colored. The age of the wasp is determined by examining the progressive pigmentation of the transverse apodeme, which is located at the base of each sternum. The youngest wasps have no pigmentation, middle aged wasps have brown coloring, and the oldest wasps have black coloring. Parachartergus fraternus nests are covered by a protective envelope which characterizes this species. The envelope often has only one opening to the soil which protects against ants, the wasp's main enemy. The wasp envelope is gray and constructed of long fibers. It is also single sheeted and has horizontal ridges. Peduncles are usually 6 mm wide and 7 mm long and are composed of vegetal fibers that are attached to the base of the nest with saliva. The nests have several layers of cells that are fixed to leaves or branches that branch out to a lateral stalk. The openings to the cells in the nest are directed downwards and have hexagonal walls. Although the sizes of nests vary, the diameter of these cells is usually around 4 mm while the height is around 10 mm. Some colonies have two combs with 98 cells while others may have 12 combs with 1751 cells. Parachartergus fraternus is found throughout Central and South America. There is a large density in southeast Brazil, especially in São Paulo state and Minas Gerais state in Matias Barbosa municipality. Nests are usually close to the Brazilian savannah, which is called the cerrado. This wasp species also has a large presence in Costa Rica. P. fraternus wasps typically live in second growth tropical dry forests. A second growth forest is a forest that has regrown after a major disturbance. These wasps build their nests by pasture fields, in roadside areas, and in urban city areas as well. Nests are often directly attached to the smooth surfaces of tree trunks, branches, and walls. Usually new colonies are formed by older individuals who swarm and create a new nest. The young P. fraternus queens stay behind to keep the older nest alive. The colony cycle begins with a pre-emergence period, which occurs before the emergence of the first offspring. Pre-emergence colonies have mostly older individuals. After this, the post-emergence period occurs which is the whole duration of the colony cycle following the appearance of offspring wasps. Next, is the pre-matrifilial phase. This is the first part of the post-emergence period and occurs when subordinate foundresses are still present in nests, interacting with worker wasps. Following this period is the matrifilial phase, which comes after the disappearance of all subordinates. Colonies now consist of only the queen and her workers. Lastly, there is a reproductive phase, where reproductive offspring (gynes and males) are born. Gynes start emerging from nests around early February; thus any female collected from colonies up to the end of January of each season will most likely be a worker. The colony cycle is usually annual, with foundress females beginning new nests in the spring after having overwintered for about 4.5 months. Despite the age of the colony, castes are almost always indistinguishable. Caste totipotency exists where all individual wasps are totipotent. Totipotency is the ability of a single cell to produce all of the differentiated cells in an organism. Therefore, one young wasp could turn out to be a queen or a worker. So, caste determination is dictated post-imaginally (pre-adult determination). In Parachartergus fraternus, the reproductive females resemble non reproductive females: there are not many physical differences. Based on morphology alone it is difficult to distinguish between castes. There is evidence for caste flexibility in Parachartergus fraternus. Intermediates may be potential queens but also perform some worker activities early on in their lives. Caste can only be determined by ovary examination and insemination data. Queen wasps were determined by the amount of sperm they had in their spermatheca (inseminated or not). Intermediate females were defined as females with some ovarian development, and workers have no ovarian development. Intermediate is not considered its own caste, though. Many females had fully developed ovaries but were not inseminated. There seemed to be little difference between these females and queens other than insemination. However, when non-inseminated females were more common, inseminated females had more developed oocytes. In some colonies, queens were slightly bigger than workers in several characteristics, but in others they were smaller. In most of the colonies, intermediates did not differ in size from queens and were usually a bit larger than workers. Caste differences seem to be more obvious as the colony ages. The differences in P. fraternus castes vary according to colony cycle. In a pre-emergence colony and one of the two worker-producing colonies, queens were larger in body size than workers, while smaller in one of the two male-producing colonies. Females can potentially become either queens (reproductives) or workers (non-reproductives) according to intracolony and environmental factors.