The Black hover wasp, Parischnogaster alternata, is a eusocial wasp in the genus Parischnogaster. It is native to South-East Asia, and builds its nests in cavities located in dark and damp locations. The nests of Black hover wasps are often found in clusters, which serves as a passive defense mechanism against predators. The annual colony cycle begins with nest initiation by a single foundress though colonies typically consist of 2-3 associative females and helpers that aid in brood development, nest construction, and colony defense. Indicative of the name, female P. alternata are known to strategically hover near nests when visiting other colonies before landing. These intrusions produce responses ranging from aerial fighting to cooperative food sharing.
Taxonomy and phylogeny
Parischnogaster alternata was originally named by Shoichi Francisco Sakagami in 1969. P. alternata is one of ten species in the genus Parischnogaster. In current literature, P. alternata has been classified as potentially synonymous with another species, Parischnogaster timida discovered by Williams in 1928. These two synonymies may result in future renaming of the species. The closest relative is Parischnogaster striatula. In a phylogenetic classification study, P. striatula was misclassified for P. alternata suggesting close genetic relatedness. These two species are both a part of the striatula-group due to shared descriptive characteristics such as the length and width of the petiole and the separation of the clypeus from the eye.
Description and identification
The Black hover wasp is characterized by their brown-black coloration. Similar to other species in the Stenogastrinae subfamily, P. alternata can be distinguished by their significantly narrow mandibles. Another descriptor is the long, pointed clypeus separate from the eye shared by Parischnogaster striatula.
Distribution and habitat
The Black hover wasps inhabit the tropical rain forests of two Southeast Asian countries: Malaysia (Sarawak and Sabah) and Singapore.
P. alternata builds dense clusters of nests in dark, damp cavities including caves and man-made structures such as vaults under bridges, water pipes, and the ceilings of grottoes. The nests of P. alternata typically appear brown with grey and pale bands due to the use of mud and vegetables. The composite materials of the nests include a mixture of mud, sand, and plant hairs. The nests are cylindrical in shape with a size ranging from 1.5 cm in diameter and 6.5 cm in length. Similar to other species in the Stenogastrinae subfamily, the nests contain a low number of cells with a maximum of 35 total. There are two known types of nests based on location. The most common type is built on flat surfaces and the other type hangs from thread-like suspensions from ceilings.
Colony cycle
P. alternata colonies are small typically consisting of no more than 2-3 females. Unlike the annual colony cycles of temperate wasps like Polistes, nesting and initiation of a colony occurs throughout the year. Typically, a single foundress initiates the colony cycle by locating a suitable site and building a nest. The foundress will build cells within the nest and lay one egg in each. Once the eggs hatch, the foundress feeds the larvae. The time of brood development is currently unknown but likely averages between 44 and 53 days based on close relatives P. nigricans and P. mellyi respectively. Some nests contain 2 or more overlapping subgroups (eggs laid around the same time), indicating that the average reproductive span of the dominant female may be short. After developing into adults, the offspring may either leave the nest to build their own or stay behind to become helpers. Unrelated females may also join the nest at any time during the colony cycle but current nest mates may resist the joining of foreign females. Although some colonies consist of more than one female (usually a helper or relative), the production of offspring is nearly always the responsibility of the dominant female.