These are some of the kinds of midges
(1) that are easy to identify from pictures. The list is deliberately simple rather than complete. The combinations of characters I list are sufficient to identify the associated genus or species. The converse is not true -- some midges of the genus, species, or subfamily may have different markings and can't be identified by this article. If multiple features are listed they all must be present. For example, I describe
Tanypus in terms of wing spotting but one species has clear wings; many species have a dark band in the middle of the wing but only a few have the full set of features listed for
Stenochironomus.
Most midges do not have marked wings. The ones that do are overrepresented here because wing patterns are easy to see in pictures. Most of the midges of subfamily Tanypodinae have been IDed to genus because the common kinds tend to have distinctive features.
Wing veins are labeled here:
Vein R2+3 may not be visible -- sometimes it is missing, more often it is too faint to see in a picture. The label R-M in the left picture refers to the nearly horizontal vein to the right of the label. If there is a vein in the empty space under the label it is the M-Cu crossvein. Crossveins and forks in veins are often surrounded by dark patches. The dark spots in the right picture cover R-M.
Is it a midge?
This is about family Chironomidae. I assume you already figured out that you have a picture of a midge. Their appearance is fairly distinctive. The most similar family with which they are confused is Chaoboridae
(2), which can be recognized by the wings held overlapping flat over the abdomen, pale color often with brown spots, and distinct rings of hairs around the antennae when hairs are present
(3).
Some of what follows is only true in North America.
Subfamilies
The common subfamilies are Chironominae and Orthocladiinae. Tanypodinae is next, and Diamesinae, Prodiamesinae, and Telmatogetoninae bring up the rear. The last lives in salt water and is found only along the ocean shore.
If the midge is holding both legs above and in front of the head, it is probably subfamily Chironominae
(4). If the first segment of the front tarsus
(5) is longer than the front tibia
(6) and the wings lack an M-Cu crossvein it definitely is. (The last two characters together are good enough if the legs are in a funny posture.)
If the midge does not have an M-Cu crossvein, the first segment of the front tarsus is distinctly shorter than the front tibia, and the front legs are held against the ground it is subfamily Orthocladiinae
(7).
If you see a midge in winter it belongs to Diamesinae or Orthcladiinae. Winter means routinely below freezing temperatures, not sweater weather in Florida. Winter midges are broadly similar due to convergent evolution. For example, they are black to absorb sunlight. Diamesinae have an M-Cu crossvein but it can be hard to see.
If R2+3 is connected to R1 by a crossvein, or R1 splits off a fork in the general direction of R2+3, the midge belongs to subfamily Tanypodinae. Very often the wings are spotted and the general color is brown or a dark or yellow green distinct from the more common varieties of midge. The connecting vein is under one of the dark spots in this picture:
Tanypodinae often have an oval pit in the thorax, as in this picture:
This feature seems to be unique to the subfamily. Some
Orthocladius have a much smaller pit.
Distinctive genera -- Chironominae
Axarus females can be recognized by a narrow black stripe behind their head and tan markings on green, as in
Stenochironomus are recognizable by color, wing markings, and the black spots near the tip of the abdomen.
Stictochironomus are recognizable by a pale band near the end of the otherwise dark femur, a dark band in the middle of the middle tibia, a dark patch over the R-M crossvein, and a dark abdomen with light rings.
If a midge of subfamily Chironominae has a dark patch at the front of the thorax divided by a pale stripe, it is one of two species of
Chironomus.
Distinctive genera and species -- Tanypodinae
Ablabesmyia are recognizable by the general color, wing spot pattern, and three brown bands on each tibia. They can be identified to subgenus based on a combination of wing and tibia markings.
Psectrotanypus dyari. Brown to dark green. Dark band across middle of wing. Dark band across end of wing reaching wingtip, possibly faint at tip, with small clear patches within, matching the pattern below.
Paramerina fragilis.
Brown with wings marked approximately as shown below. The wing markings are made of dark hairs, not pigment, and have a distinct texture.
Tanypus
Brown color, a row of five dark spots in the wing between the R and M veins, some split in half by the "false vein" running down the middle of the wing, one of them possibly faint. Possibly a raised light colored bump in the middle of the thorax. The M-Cu crossvein intersects Cu before the fork. One other species of Tanypodinae has a superficially similar wing with M-Cu meeting the fork in Cu.
Distinctive genera -- Orthocladiinae
The common varieties of
Cricotopus can be recognized by the white band on the front tibia and three yellow bands on a black abdomen.
Chasmatonotus has a black wing with at least one large white spot or band and a large trench down the middle of its back. The genus mates on the ground. Males of ground-mating midges generally do not have long, fuzzy antennae.
