Polistes metricus (metric paper wasp or metricus paper wasp) is a wasp native to North America. In the United States, it ranges throughout the southern Midwest, the South, and as far northeast as New York, but has recently been spotted in southwest Ontario. A single female specimen has also been reported from Dryden, Maine. Polistes metricus is dark colored, with yellow tarsi and black tibia. Nests of Polistes metricus can be found attached to the sides of buildings, trees, and shrubbery.
Like other Polistes species, P. metricus, has evolved eusociality and demonstrates behaviors including nestmate discrimination and local mate competition. Like the other members of the order Hymenoptera, Polistes metricus has a haplodiploid genetic system. Nests of P. metricus have distinct characteristics like the ability to share nests with other Polistes species and reuse nests multiple seasons. Another distinction is that Polistes metricus foragers take off from their nests depending on how long their trip will be. For short flights, they exit the nest flying horizontally, while for long flights, they exit the nest flying straight up into a high altitude before pursuing their direction.
P. metricus prefers to use soft-bodied prey, especially caterpillars, to feed their larvae.
Taxonomy
This species was described by Thomas Say in 1831. Rau referred to this species as Polistes pallipes or P. fuscatus pallipes in a number of his publications. However, references to P. metricus as either P. pallipes or P. fuscatus pallipes are due to confusion with a dark morph of P. fuscatus, so the name P. pallipes is rather retained as a synonym of P. fuscatus and not of P. metricus.
P. metricus is found to be most closely related to P. carolina. The most recent phylogenetic analysis shows that both share a common ancestor with P. bellicosus.
Description and identification
P. metricus has a dark ferruginous (rusty) color with black markings on its thorax and a mostly black abdomen. Its tibia is black, and the tarsi are yellow. A black spot, separate from the antennae, contains the three ocelli. Females bear six abdominal segments, while males bear seven. Swelled parts of the abdomen of this species are a key defining element.
In the female, extensive rust-red coloration occurs on her head and mesosoma. Female P. metricus yellow markings are very limited in area. The mesosoma has a large spread of red color, and the metasoma shows black coloration. P. metricus also has an especially marked outward bend in sternum 2; however, this is often a very subtle characteristic. In the male, the red coloring takes up less area, but black coloration takes up more area. The male has more yellow markings than the female and a yellow color on his entire face and the pronotal carina. The yellow coloration on the legs of the male is highly variable in this species.
The smallest of the larvae can be told apart from eggs by noticing the darker anterior end of larvae. In the nests of P. metricus, cells that are capped are most likely cells that contain pupae. After pupae emerge from their cocoons, they leave behind evidence of their metamorphosis in the form of cocoon shavings.
Distribution and habitat
The distribution of P. metricus is largely limited to North America. P. metricus has been spotted in the far southwestern reaches of Ontario, Canada. In the eastern United States, one female was seen in Dryden, Maine and recorded by the Canadian Nursery Certification Institute for pest control. This was a novel sighting for Maine, and probably indicated the beginnings of the spread of P. metricus into Maine. Other states where P. metricus is known to be located are on the east coast of the US, including New York, Pennsylvania, and the area from the southern part of Michigan all the way south to Florida; and the area westward to Nebraska, Kansas, Oklahoma, and the eastern part of Texas. Specifically, P. metricus has been studied in Brazos Bend State Park in Texas along with other wasp species, including Polistes bellicosus.
Preferred nesting sites
P. metricus chooses its nesting sites based on shelter from the elements, size, lighting, and sources of water. It tends to build its nests in sheds and barns and on the underside of eaves. It especially prefers large and well-lit nesting locations. Its nests are mixed with those of P. fuscatus on a regular basis, and locations where one of them is present tend to also contain the nests of the other species, in close proximity to each other. P. metricus likes to use large bodies of water, such as ponds, as sources of water. In the summer, they frequently make trips to water sources for hydration.