Polistes carnifex

May 23, 2021 Features / Columnists, Interesting Creatures in Guyana

Kaieteur News – Polistes carnifex is a neotropical vespid wasp in the cosmopolitan genus Polistes, known for its extremely painful and potent sting. The wasp is native to Central and South America. It is a very large yellow and brown paper wasp that establishes small colonies which build nests under the eaves of buildings or suspended from branches. The colonies are founded by solitary queens. Not all nests have a female with developed ovaries. Foraging adults bring nectar and macerated prey back to the nest to feed to the developing larvae which are individually housed in separate cells in the nest. It has mandibles with teeth.
It is the largest Neotropical wasp in the genus Polistes with a body length up to three centimetres. The normal size is 24-27mm, with a possible maximum of 33mm. Despite its size, it is a relatively non-aggressive insect.

It is coloured yellow with some brown stripes, these are partially blackish. The antennae are yellow with a darkened base. The head is yellow, the crown of the head being black and ending with reddish-brown stripes. The maxillae are reddish-brown, outlined in black. The thorax is yellow, the dorsal part black, but with a quartet of dark reddish-brown spots. The pronotum is totally or almost totally coloured yellow. The abdomen is yellow, the second segment (tergite) darkened at the base. The wings are reddish-brown, or yellowish reddish-brown, and the feet are dark-coloured.
It can be grouped with a number of species which can be distinguished from other species within the genus Polistes by their lacking of a groove on the underside of its head called the epicnemial sulcus. P. carnifex can be distinguished among this group of wasps by its wide cheek plates. Also the first tergite is very compact, dorsally convex, and elevated vertically compared to the constriction where the abdomen is inserted into the thorax. Furthermore, the eyes do not touch the clypeus. Lastly, this is a very large wasp, with individuals always longer than 20mm. The first gastral segment (sternite) is less broad than long.
As a member of the order Hymenoptera, Polistes carnifex has mandibles, which may be used to obtain wood fibers, build nests, or capture and macerate prey. The mandibles of P. carnifex are short. Yet, they are markedly wide at their base, with a length to basal width ratio of approximately 2:1. An external basal area stretches “from the basal margin … to a point situated about half-way the mandible’s length.” P. carnifex also have teeth. “A convex distal posterior area … is continuous with the posterior-most apical tooth and stays adjacent to a distal media area”. This area is convex in P. carnifex. In P. carnifex, the third tooth’s anterior edge is elongated, compared to in other species.
Like most insects, the genitals of this species are very characteristic. The male wasp has a paramere that is two and a half times as long as wide at the middle, with the parameral spine about 1/6th of the length, and a shallow groove at its side. This spine is covered in very long and dense bristles and pointed apically. The paramere lobe is well developed and rounded, the lower part of the paramere is narrow, about 2/3 the width at the middle part.
It has a slender aedeagus, with about 27 teeth distributed from the end to beginning of the expansion in the middle part of the aedeagus. The penis valve is weakly dilated, with a central entrance and a weakly bi-lobed appearance (the valve being a little more than 1/3 of the length of apical part of the aedeagus). The expansion of the middle part of the aedeagus is well developed and has a pointed apex. The lateral apodeme of the aedeagus is directed forward with a weak central projection and shorter than the rounded ventral process (projection), while the inferior (lower) portion of the aedeagus is weakly curved -appearing almost straight from the side.
The digitus is slender, with a well-developed apical process which is about one and a half times longer than the base of the digitus and the same width from the base to the end. This end (apex) is pointed. The digitus has a band of obvious punctation around its base, and an anteroventral lobe that is short with a rounded end, and is covered in easily rubbed off (evanescent) bristles.
The cuspis is slender, with an apex which is pointed and tapers abruptly, and covered in long and sparse bristles, with more bristles found at the edges of the sides, and with short bristles on the lower part. The punctation on the cuspis is only found on the lateral lobe. (Source: Wikipedia)

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