Synonyms and other taxonomic changes
Polistes carolina (Linnaeus, 1767) (=Vespa carolina)
Polistes rubiginosus Lepeletier, 1836 (=
P. perplexus,
P. generosus)
(1) Identification
These two mostly red species often can only be told apart under the microscope and were formerly considered synonymous in older literature. There are two primary structural differences that are reliable, different nesting tendencies, and a few trends in coloration that are useful for some individuals (most useful in males).
Note: for the associated comparison images,
P. rubiginosus was previously known as
P. perplexus.
(2)
Malar space and genae - one key difference in females (but not males) is in the density of hairs, or pubescence, on the wasp's
malar space and
genae, or the "cheek" region. In
P. carolina, this region is largely bare apart from scattered, larger hairs (macrosetae). In
P. rubiginosus, this region is much more thoroughly covered in fine, short, silvery hairs. For a side-by-side comparison of the two species see
here.
Facial hairs on a female
P. carolina
Propodeal ridges - a key differences in both males and females is the difference in size and number of ridges on the
propodeum, or the rear slope of the thorax. In
P. carolina, these ridges are either fine or entirely absent, resulting in an overall smooth appearance. In
P. rubiginosus, these ridges are consistently coarser, resulting in a more ribbed appearance. For a side-by-side comparison of the two species see
here.
Photos displaying ridging in
P. carolina (left)
P. rubiginosus (right), best viewed at full size.
Nesting - Nesting trends are not necessarily diagnostic but may give some useful clues. More typically, P. carolina nests in open areas such as the eaves of buildings. On the other hand, P. rubiginosus often nests in hollowed out spaces, such as hollow tree trunks, outdoor pottery, and birdhouses.
Open nesting in
P. carolina (left) and enclosed nesting in
P. rubiginosus (right)
Coloration - Coloration only works in separating males and certain color-extreme females. For
P. carolina males, the
scutum, or central shield-like plate of the thorax, is almost entirely red, lacking any black markings (caution: sometimes dark internal tissue may shine through the red cuticle, giving a false impression of dark coloration). In
P. rubiginosus males, the scutum is consistently and conspicuously black-marked. Female coloration overlaps considerably, with both species often being entirely, or nearly so, red. Color-extremes of female
P. carolina may be noted for more prominent yellow markings, often including a single yellowish ring on the first abdominal segment. Blackish markings are typically absent or so restricted to sutures between plates of the exoskeleton, a restricted mark around the
ocelli, and occasionally a faint line down the center of the scutum. Color-extremes of female
P. rubiginosus may be noted for more prominent black markings, particularly on the thorax, where the scutum often has black markings around the exterior and interior, outlining two variably-sized, occasionally connected red lines. Yellow markings are typically absent, with light markings restricted to the propodeal valves and tarsi.
Male
P. carolina (left) and
P. rubiginosus (right)
Color-extreme female
P. carolina (left) and
P. rubiginosus (right)
