Parischnogaster alternata

Although one female typically dominates the reproduction on one colony, there is strong evidence for co-foundress behavior among P. alternata. Occasionally, the founding of new colonies occurs from the cooperation of two or females. The females stay on the nest for a good portion of the day but rarely interact. Both co-foundresses contribute to the construction of the nest and overall protection of the colony. Though the associated females share many responsibilities equally, there is evidence that female foundresses with larger ovaries spend more time off the nest, indicating some type of hierarchy based on reproductive ability. One advantage in associative nesting is increased offspring. The more foundresses present in a nest, the more cells and eggs are produced. Also, the presence of more than one female improves active defense of the nest.[12]

In P. alternata, some developed brood will stay behind to become helpers instead of finding their own nest.[12] Through cooperation with relatives, species can enhance the local resources surrounding them by becoming helpers. The advantage of helpers increases on high quality territories.[5] The helpers can contribute to the defense of the nest from predation or usurpation.[12]

Unlike associate females or co-foundresses, helpers typically share genetic relatedness with the foundress. Female helpers indirectly obtain benefits in fitness because the reproductive duration of the foundress is relatively short. Thus, the line to become the next dominant is not long. Many female helpers possess fully developed ovaries and the ability to produce male and female offspring. This anatomical feature of helpers may be indicative of a selective trait for preparedness for when the current dominant female stops reproducing.[12] Most females will become egg-layers whether on a new nest or their natal nest.[4]

Visitations from members of other colonies occur frequently in P. alternata. A few known reasons for visitations can include becoming a new, often non-related helper, sharing of food, stealing eggs or abdominal substance, and feeding on drops of fluid on patches. When there are already a lot of female residents, the reaction of rejection increases.[6] P. alternata females utilize different nest defense tactics against intruders such as Liostenogaster flavolineata. If the wasps suddenly land, the nest residents may leave and return after a few moments and fight who ever remains. Although some Steronigastrinae wasps partake in antennal combat, P. alternata rarely use this fighting method and instead initiate falling fights. By nesting in clusters, P. alternata improves the collective defense against predation or social parasitism.[6]

One of the most interesting behaviors of species of Parischnogaster is the egg deposition process. The ovipositing female uses an abdominal substance produced by herself to handle the egg. In the first stage, the wasp collects a patch of viscid abdominal substance in her mouth. The patch is then placed into the cell. In the second stage, the wasp bends her abdomen towards her mouth. As the egg emerges from the abdomen the female will grasp it with its mouthparts. The final stage consists of collecting another patch of abdominal substance to place on top of the egg in the cell. This process may have evolved for defense purposes. Since P. alternata typically take on flight as an active defense, this method helps the female save the egg they are laying if disturbed by an attack.[12]

Similar to other Stenogastrinae, the major predators of the Black hover wasps are ants, ichneumon flies, and Vespa hornets, specifically Vespula tropica (which has also been found to be a major predator of a number of Parischnogaster species, such as Parischnogaster mellyi and Parischnogaster nigricans serrei). Hornets often visit the nests of P. alternata and extract pupae and large larvae. While the colonies are relatively small, the presence of helpers and co-foundresses contributes to active defense tactics. Females may attempt to attack hornets in flight by stinging. Through cooperative defense, some residents drive away the hornets while the wasps fall from the nest in order to save the adult individuals. Nonetheless, evolution has decreased active defense mechanisms of P. alternata. Thus, the attempts to attack predators often have little to no effect.[3]

Due to the small colony sizes, P. alternata have limited capability to defend the nests. Thus, the Black hover wasp construct nests in such a way to blend in with the forest vegetation. The camouflaged nests help reduce predation by serving as the major line of defense.[3] The foundress responsible for making the nest searches for the materials and builds the nest, though some have already been built. The two major types of nests are the hanging nests and the flat-topped nests. The hanging nests are slender in shape in comparison to the flat-topped nests that are more stout and oval-shaped.[11] The hanging nests provide a protective screen that potentially block predators.[3] P. alternata utilize both organic and inorganic materials. The inorganic materials vary based on region but demonstrates the use of man-made materials. The organic composite materials of the nests include a mixture of mud, sand, and plant hairs. These materials contribute to the pale brown color of the nests allowing them to blend in with surrounding trees and plants.[11]

Seemingly working against efforts of mimicry, P. alternata often construct nests in clusters, which potentially attract attention due to size. Clusters are defined as the aggregation of a multitude of nests consisting of different colonies. Two majors reasons for clustering include reduced predation due to the dilution effect and improved hunting. Clustering can increase overall fitness of the colony because cooperation results in an increase in finding food.[3] The dilution effect assumes that by aggregating in a larger group, the chances of predator attack are significantly reduced. In addition, the theory proposes that individuals will seek center positions in the group to further reduce their chances of attack.[13] There is evidence that the core clusters of P. alternata nests often have greater visits from conspecifics and consequently greater defense. The central core comprises older nests surrounded by younger colonies. The more densely packed clusters attract more predation due to a decrease in conspicuity but the predation rate is lower. It is assumed that the advantages of passive protection from predation served as a major evolutionary factor that resulted in nest clusters in P. alternata.[3]

Cluster of Parischnogaster alternata nests