Polistes annularis

Polistes annularis (P. annularis) is a species of paper wasp which lives throughout the Caribbean and in parts of North America. Its species name is Latin for 'ringed' and it is known for its distinct red body color. It builds its nest under overhangs near bodies of water that minimize the amount of sunlight penetration. It clusters its nests together in large aggregations, and consumes nectar and other insects. Its principal predator is the ant, although birds are also known to prey on it. It is a primitively eusocial wasp, meaning that all individuals develop the capacity for reproduction, regardless of social caste. This primitive eusociality has been seen in bees as well, including the sweat bee, Lasioglossum zephyrum. As such, P. annularis demonstrates behavior typical of other polistine wasps, and has a dominance hierarchy, relatively small colony size, and a female-biased sex ratio. Unlike other wasps, P. annularis is relatively robust in winter conditions, and has also been observed to store honey in advance of hibernation. It is closely related to P. major, P. buysonni, and others in the subgenus Aphanilopterus, and slightly less related to the more common P. bellicosus, P. carolina, P. metricus, and P. fuscatus. While many other North American Polistes species show sexual dimorphism in coloration, P. annularis and P. erythrocephalus do not. This species differs from P. metricus in terms of the coloration of the antennae and thorax. There is geographical variation in coloration between northern and southern populations. In the north, the thorax of P. annularis has ferruginous (rust-red) markings on a predominantly black background, while in the south, the thorax is mostly ferruginous, with black markings. The legs also vary from black to ferruginous. In terms of size, the fore wings are 18.5–23.5 mm (0.73–0.93 in) long in females, and 17.5–19.5 mm (0.69–0.77 in) long in males. Both males and females are red-faced, which makes intersex determination less straightforward; however, it also makes it easier to recognize members of this species compared to other closely related species. Its initial metasomal segment is narrow, a feature that it has in common with P. bahamensis. P. annularis is very similar in appearance to P. bahamensis. To distinguish P. annularis from P. bahamensis, one should notice that P. annularis has no yellow mark on its mesopleuron and usually also has no yellow apical tergum band. In addition, its mesosomal yellow markings show less development. Within the P. annularis species, reproductives and foundresses can be readily distinguished, as well. Reproductive females can be recognized visually because their wings are unworn, since they do not forage much (unlike the workers). In their abdominal cavities, large amounts of white-colored fat are stored beneath the intersegmental membrane. Foundresses can be discriminated from workers on the basis of their differential behaviors. Nests can be identified by their paper material and the way their cells are openly exposed to the external environment. P. annularis is also classified as a primitively eusocial wasp, which means that all individuals develop the capacity to reproduce over their lifetimes, whether or not they actually do so. The mandible is the insect organ for biting and crushing, analogous to the jaw in mammals. In the genus Polistes, the lateral mandibular groove is smaller in size than in other genera of social wasps. A common misconception is that the mandibular gland is the anatomical portion shaped like a sac. In actuality, the sac formation is the gland reservoir that feeds into the gland itself. The actual gland is pressed up against the sac surface. Gland cells are shaped like polygons. Like poisonous structures in formicine ants, gland cells are continuous with the gland reservoir, but no filaments extend from the gland or sac as they do in the ants. The sac is closest to mandible’s medial portion. A duct exits the sac. The duct opening is encircled by a sphincter muscle controlling the gland’s secretions. The duct is opened by sclerotized bars in conjunction with the hypopharynx. When the hypopharynx moves, pressure forms on the opening of the duct via the bars. When the bars dissipate this pressure, the duct closes. The nest pedicel, which is the stalk by which the entire nest hangs from the horizontal face of the overhang, is made from a durable material composed of the wasps’ oral secretion. It has a nitrogen content of 11% and is mainly carbohydrates and proteins. Pedicel proteins are rich in glycine, proline, alanine, and serine. These amino acids are also found in the silks of other insects. Another minor component is N-acetylglucosamine, which is probably bound to the pedicel protein. Proline is a major component of structural proteins and likely contributes to the structural strength of the pedicel in holding up the rest of the nest. The pedicel suspends the nest high in the air and precludes many predators from getting close to the nest. However, birds often try to knock nests off the cliff, and colonies that hang low toward the ground can be attacked and eaten by raccoons. Cellulose makes up most of the nest paper. Larval silk is a protein with high amounts of serine and alanine. When larvae mature, silk is produced in their labial glands. Larvae spin cocoons that enclose themselves into their cell in the nest. Members of P. annularis have cuticular hydrocarbons on the surface of their bodies that may serve as social recognition factors. These are composed of a complex mixture containing dimethylalkanes, n-alkanes, and monomethylalkanes. They are straight-chain and have methyl branches. The most common chemicals are 13,17- dimethylhentriacontane (18%) 3-methyl-nonacosane (13%), 3-methylheptacosane (11%), and n-heptacosane (8%). These serve to protect the wasps from dehydration. Their composition tends to be unique to each species of wasp. Hydrocarbons are present on the surface of workers, males, eggs, and larvae, as well as the surface of the nest and its pedicel. The lipids in the nest paper probably function in kin recognition among workers, while those in the pedicel likely deter predators. The free fatty acids of the pedicel induce the necrophoric response in ants, which causes them to avoid the pedicel rather than cross over it and prey on the nest’s inhabitants. In ants, the necrophoric response is defined as the behavior of recognizing dead colony members and carrying them to a refuse pile away from the nest. Adult males have the hydrocarbon compounds as the workers, but they are present in different amounts. In males, the most common component is 3-methylnonacosane (21%); in eggs, 3-methylnonacosane makes up 23% of lipids; in larvae 13- and 15-methylnonacosane are the most common (15%). Nest paper and pedicel have much larger hydrocarbon units, between 27 and 31 carbons in length. The pedicel also contains hexadecanoic acid and octadecanoic acid. P. annularis has been used as a model species to investigate the power of microsatellite markers in maternity assignment of social insects. Historically, maternity assignment has been problematic in social insects for several reasons: 1) Possible mothers are usually related so their offspring are highly genetically similar. 2) The real mothers may already have died, increasing the risk of assigning offspring to the wrong surviving mothers. 3) The father’s genome is inaccessible because males mate and die before their offspring are even born. Microsatellite markers have been demonstrated to nullify these problems in P. annularis. They are single-locus, codominant markers that vary dramatically for number of simple sequence repeats. They can be readily amplified using the polymerase chain reaction, and the samples of DNA can be minuscule. This allows scientists to access the genotypes of very young embryos and even sperm from spermathecae. Through the genotypes of stored sperm, alleles of dead fathers are recovered. They can then combine these data with the maternal genotype to improve the accuracy of the maternity assignment. The first description of P. annularis was published by Carl Linnaeus in his 1763 Centuria Insectorum, where he named the species Vespa annularis. It was moved to the genus Polistes by Johan Christian Fabricius in 1804, two years after Pierre André Latreille had erected the new genus.