Dolichovespula adulterina

''Dolichovespula adulterina'' is a species of parasitic social wasp found in the Palearctic region. ''D. adulterina'' feeds on a variety of foods, including insects, spiders, arthropods, meat, molluscs, fruit, nectar, and larval secretions. ''D. adulterina'' was formerly considered to be synonymous with ''D. arctica'' from the Holarctic region, but more recent research indicates that ''D. arctica'' is a separate species.

Taxonomy and phylogeny

''D. adulterina'' is a parasitic wasp in the order Hymenoptera. It is a member of the subfamily Vespinae and was labeled a subgenus of the genus ''Vespula'' at one point. ''Dolichovespula'' spp. are identified by a gently notched labrum on the ventral border. This is the location of sensory bristles. ''Dolichovespula'' spp. exhibit microscopic spinous growths all over the palate region, whereas other species have localised growths. Another distinctive feature is the monodentate mandible, where the primary incisor is always linear. Its body size is nearly identical to species of'' Vespula''.

Identification

The length of the forewing is 13.0–14.0 mm in females and 10.0–12.0 mm in males. Commonly, its body is an ivory colour, but it can be pale yellow on occasion; the pale yellow subspecies are found in the western Nearctic and Palearctic regions. Usually, the clypeus is elongated, but sometimes it will be small and round. Females almost always have a black, disc-like spot, whereas males have a black mark that extends to the ventral margin of the clypeus. Melanic individuals have a black spot extending to the dorsal margin. The postocular band in females is narrower relative to the lateral postocular stripes, whereas in males it is rarely narrowed. Occasionally, small ivory sports are located on the pronotum behind the pronotal fovea. Females present with pairs of black discal spots on tergum 5, and occasionally on terga 3 and 4, as well. In males, tergum 6 usually is black with a less developed fascia than previous terga. Furthermore, in males, tergum 7 is usually black and rarely contains two ivory spots.

A black and white, sometimes pale yellow, this wasp has brown-tinted wings. Normally, abdominal segments 1-5 are bordered, towards their rears, with a thin, white band. The large, dark malar space between the eye and the yellow jaw puts this species in ''Dolichovespula'' rather than the related genus ''Vespula''.

Distribution and habitat

''D. adulterina'' has a Palearctic distribution, and it parasitises '' D. saxonica'' and '' D. norwegica''.

''D. saxonica ''constructs nests in trees and shrubs no more than 2 m above the ground. Sometimes, ''D. saxonica '' nests in beehives, underneath overhanging edge of roofs (sometimes up to 7 m above ground) and porches, and cavities of walls. On occasion, they may also nest in tree holes or holes in the ground.

Biology

''D. adulterina's'' main host in Europe is ''D. saxonica'', but it also parasitises ''D. norwegica''. This species produces no workers; the eggs laid in the host's nest produce queens and males, which are nurtured by the workers of the host species.

Colony cycle

''D. adulterina'' is a parasitic species, so its lifecycle is consistent with the host it parasitises. Furthermore, ''D. adulterina'' invades the nest of host species before the first set of workers appears, and lives alongside the queen for a time before usurping her.

''D. saxonica''

''D. adulterina'' most often parasitises ''D. saxonica''. In mid-May or just before, colonies initiate. The first set of workers emerges in early June and begins working on large cells mid-June. Queens emerge in early July and the colony continues until just after mid-August.

Regardless of the host species, the queen ''D. adulterina ''invades the host colony around the same time that the first workers start to emerge. The invasive queen waits around 10 days before killing the host queen and laying her eggs. Males emerge in late July and new queens emerge in early August. After a few days, the males and females leave for their mating flights. The colony then terminates in mid-August. The inquiline queen dies by mid-July, if not earlier, from fights with host workers. After the colony ceases, the queen enters hibernation in a sheltered area. She will then emerge and feed on nectar and malaxate arthropods until she attempts to usurp a host colony. On average, the colony cycle for a successful parasitic queen is about 2.8 months.

Parasitic behaviour

''D. adulterina'' is a parasitic social insect. Social insects are labeled parasites when the parasitic female enters the host nest and assumes the reproductive responsibility of queen while simultaneously leading the pre-existing workers. ''D. adulterina ''is an inquiline species, meaning that workers are not produced. One of its hosts species is '' D. norwegica'', although this was not accepted by some authorities for some time, indirect evidence was the presence of ''D. adulterina'' in regions where ''D. saxonica'' was absent but the related ''D. norwegica'' was present and this was confirmed by direct observation. Furthermore, they do not have a worker caste and they do not construct nests. Instead, they will use the host nests and workers to raise their offspring.

''D. adulterina '' uses a submissive approach while the host nest is under attack, living alongside the host queen for a while before attempting to kill her. This is different from other inquiline species, such as '' V. austriaca'', which attack the nest's queen immediately. During its time in the nest, ''D. adulterina'' is an active member of the colony, feeding larvae and constructing portions of the nest. Workers of the host species were observed interacting with ''D. adulterina'', suggesting that the parasite may emit a chemical that pacifies the host. This is also supported by the presence of an enlarged Dufour’s gland relative to other vespine species. Time of invasion also differs between species. ''D. adulterina'' invades the nest of the host species before the first set of workers appears, whereas '' Vespula austriaca'' invades after the emergence of the first set of workers.

Diet

''D. adulterina'', like other social wasps, is primarily carnivorous. The species feeds on a multitude of insects, spiders, and arthropods. To do this, adults malaxate prey and feed on the juices. Other times, they have been observed eating meat, molluscs, fruit, and nectar. Larvae produce a secretion on which adults feed, as well. Wasps limit themselves to attacking live prey, but other species have been observed to feed on carcasses. Trophallaxis is a common process among wasps, where one member transfers food to another member by feeding it mouth-to-mouth. Members of the host nest are mainly responsible for feeding the parasitic ''D. adulterina ''larvae.

Sting

''D. adulterina's'' stinger is an adaptation to its parasitic biology. The cuticle of the stinger is thicker than average and is curved. These modifications allow for ''D. adulterina ''to effectively penetrate the intersegmental membranes of the host. ''D. adulterina '' is better equipped defensively, as well. The abdominal sclerites are closer together, providing a smaller gap for incoming stingers to penetrate, thereby decreasing chances of injury.

Emery's rule

''D. adulterina'', along with ''V. austriaca'', ''D. arctica'', and ''D. omissa'', are the only four vespine wasp species that display inquilinism. Furthermore, all of these species abide by Emery's rule, which states that a parasite is more closely related to its host than to any other species. In host colonies, ''D. adulterina ''queens have allomonal control over worker wasps. While ''D. adulterina ''is able to comfortably coexist with its host, it does not integrate nearly as well into host colonies as inquiline ant species. Due to its mediocre proficiency, inquiline wasps are only able to parasitize other species that exist in small colonies and have short cycles.

References

{{Taxonbar, from=Q916125

Vespidae
Hymenoptera of Europe
Taxa named by Robert du Buysson
Insects described in 1905