Parischnogaster nigricans serrei is a hover wasp subspecies in the family Vespidae, and it is predominantly found in the Java region of Indonesia. Its nest cells are of conical structure, linearly attached to a string-like substratum. The nests are typically found in places open to human interactions, such as gardens, trees, or forests around villages. There is a clear dominance hierarchy within colonies, which often affects the behavioral activities of its members. The wasp’s most common predators are Vespa tropica, also known as the great banded hornet. P. nigricans serrei defends itself by flying away or giving out alarm calls.
Taxonomy and phylogenetics Studies investigating the biology and social behavior of subfamily Stenogastrinae wasps have begun since the early 20th century, but some of their unusual morphological and ethological traits make it hard for them to have a specific systematic allocation in the phylogenetic tree. These wasps also vary a significant degree in terms of social organization since there are some species that show a rather primitive social life while some display complex, socially dependent behaviors. Consequently, Van der Vecht classifies them as members of the subfamily of the family Eumenidae, while Carpenter considers them to be included in the family Vespidae along with Euparaginae, Masarinae, Eumeninae, Polistinae and Vespinae. Therefore, studying subfamily Stenogastrinae species has long been regarded as a way to investigate the evolution of social life in Hymenoptera due to the wide spectrum of eusociality displayed in their wasps.
Description and identification
Morphology
Parischnogaster wasps are typically 10mm long with a sub-triangular shaped head. P. nigricans serrei has a pretty uniform facial coloration, though females have more evident facial markings than males. Regarding species-specific exocrine glands, tegumental glands are clustered around the anterior part of the third gastral tergum. Additionally, male wasps have three white stripes on their tergites, which is associated with patrolling and mating behavior, but females do not display such morphological features. Males of the species can be differentiated from Parischnogater jacobsoni, their closest cousin, because male P. nigricans serrei wasps lack a knife-like spine in the center of the clypeus.
Nesting The wasp often cohabits with humans; its nests are typically found in gardens, on trees, or remains of forests around villages. Its nest structure is also rather simple; it typically has conical cells attached in a linear fashion along a string-like substructure. Materials used are exclusively of plant origin, and abandoned cells are often recycled for building new cells or enlarging existing, active cells. The nest substructure can be made up of a wide variety of materials. Some nests have been found to be attached onto plant stems, lichens, veins of dead leaves, roots, or even iron threads, cords, and electric wires. It is easy to find conical cells in pairs, and they are typically built in slight rotation relative to the previous one.
Distribution and habitat Parischnogaster nigricans serrei has been identified in the village of Tegallega, near Bogor, and in the western part of the Java Island of Indonesia. It is not disturbed by human interactions, so its nests are often found close to civilization and human dwellings. This kind of habitat choice is rather unique of P. nigricans serrei (along with Parischnogaster mellyi), since Stenogastrinae species are rarely populated in areas disturbed by human contact and civilization.
Colony cycle There are five distinct stages in the colony cycle of P. nigricans serrei: The pre-emergence period can be subdivided into two stages (foundation and initial nest), and the post-emergence period into three stages (young colony, middle-aged colony, and mature colony). Foundation: It often marks the period between the start of the first cell by a foundress and its closure. Nests are typically found by a foundress who waits a few days before laying its first egg, and after doing so, she builds an ant guard a few centimeters above the first cell. Foundresses frequently reuse old, abandoned nests, and this leads to a number of foundresses living in the same nest for a short period of time. Initial nest: When the first larva fully matures, the foundress closes the cell with identical material as the ones the original walls are made with. During this stage, the foundress limits her foraging activity and stops collecting nest material, and thus spends more time on the nest. Young colony: After approximately 45–50 days from the start of the foundation stage, the first imago, which is usually a female, appears on the nest. During the first week, the foundress is the one foraging and acquiring food, but afterwards, the role reverses and the daughter is the one who forages and spends a considerable amount of time away from the nest. Female imagines (plural form of imago) that emerge later in the stage help their mother foundress rearing the brood, usually through active foraging. Middle-aged colony: The first male usually appears after 3 to 5 females emerge in a nest. At least the first male in a given colony is a direct offspring of the foundress, and it emerges around the same time the first female emerges. The males are also very loyal to their native nests and are typically aggressive in soliciting food from the foragers. Mature colony: This stage can be defined as a point in time in which there is a break in growth in cell number (and thus the population on the nest). Therefore, an equilibrium between the number of emerging and disappearing individuals is established. If there are either fewer females than males present on a given nest, the number of cells is greater than 24, or the total number of adults is more than 10, one can say that a certain colony of P. nigricans serrei is mature.
Behavior
Elementary behaviors Elementary behaviors described in this section pertain to behavioral activities that are common to both males and females in a given colony.Turillazzi, S. (2012). The Biology of Hover Wasps. Florence: Springer. Resting: Males and females spends about half of the time resting, being completely inactive with their bodies slightly raised or flattened against the substructure of the nest. Abdominal regions are distended or slightly bent, wings are low and joined, and antennae are wide apart. Rarely do the wasps rest inside the cells, but commonly do so in between cells and ant guards. Alpha females prefers resting in the vicinity of the central cells and in the zone near the ant guards. Desire for such positions could be related to nest defense. Grooming: In some nests, grooming activity is predominantly seen around the time of sunset. P. nigricans serrei typically clean their entire body, usually beginning with hind legs, abdomen, and wings. Flight: Flight of any Parischnogaster species features complicated hovering and quick changes in terms of flight direction. With such high motility, females are able to forage small prey from webs and males can perform their aerial ritual by displaying their three abdominal stripes. Their legs are also kept very closely to their body and the abdomen is fully extended during a typical flight.
Extranidal behaviors Extranidal behavior described in this section pertains to particular behavioral activities that specifically occur outside the nest that are common in both adult males and females in a given colony. Foraging and patrolling also constitute extra behavior, but they are discussed in more detail in patrolling behavior and diet and foraging activity. Pulp Collection: Pulp is collected mainly for constructing nests, and this kind of activity is present in foundation, young and middle-aged colonies, but not very much in initial and mature colonies. This is partly due to the fact that nest construction is absent in initial nest stage and mature colonies typically reuse and recycle old cell material. Pulp collection activity reaches its peak in early morning, and it often occurs after water collection. Rest outside of the Nest: Female and male wasps also often rest outside of nests on roots or leaves. Various individuals interact with each other but no particular behavior has been recorded. Defecation: Wasps of subfamily Stenogastrinae defecate by rubbing the tip of their abdomen to the nest substructure, leaving the feces there. Since no fecal remnants are found in nests, one can assume that this activity happens externally. This extranidal defecation has been considered to be helpful in maintaining nest cleanliness and hygiene.
Patrolling behavior Patrolling activity is one of the characteristic behavioral features of P. nigricans serrei, and similar to P. mellyi; displaying their abdominal white stripes while hovering is frequently observed. However, unlike P. mellyi, they hover vertically the majority of the time instead of making horizontal shifts. A male wasp is able to switch around between multiple landmarks, and this can lead to conflicts with other male patrollers. If a landmark is already taken by a male, the newcomer hovers a couple inches behind the owner, and the owner responds by quickly distending its gaster. This display of the gaster often results in the newcomer leaving the landmark, but it can also lead to start of a contest. A typical contest usually involves a tandem flight where the two males ascend, suddenly changing position (the owner goes behind and vice versa), displaying their abdominal stripes, and eventually clashing until one of them surrenders and leaves the landmark. Towards the end of the daily period of patrolling, fewer males are left hovering the landmark, and usually those who remain till the very end are the ones who won the most contests. Male P. nigricans serrei leave their nests around 1pm, and a typical patrolling session ends around two hours after departure.
Colony maintenance behavior
Ant guard construction Ant guards are special umbrella-like structures that are built for defending against ants. Ant guard development begins around the first couple days, after the construction of the first cell, and it is typically built from material excreted from the tip of a female gaster. Small droplets of the guard material are collected on the hind legs, and they are rubbed against the extremity of the distended abdomen. Afterwards, the droplets are transferred to the middle legs, and ultimately to the mouth of the wasp. The female then applies the substance onto the nest by licking and simultaneously moving it around the structure of the guard without losing contact. This entire sequence, which lasts around 30–40 seconds, is repeated for 10–30 minutes and only takes places in the late afternoon before sunset.
Social organization