Insects of West Virginia web site
Above: Tipulid Crane Fly on the left, Limoniid on the right
Compare the antennae of the two, and also their maxillary palpi
As we mentioned on the family pages for Tipulidae and Limoniidae, there are two key traits to look for in differentiating these families. One is the number of antennal segments. Tipulid Crane Flies generally have 13 segments, while Limoniid Crane Flies has 14 or 16. While there are exceptions, this rule works in the great majority of cases.
The other trait is the length of the terminal (fourth) segment of the maxillary palpus. In Tipulid Crane Flies this terminal segment is markedly longer than the third segment. In Limoniid Crane flies the fourth segment is shorter than the third, or about the same length. In the photo above, note the enormously long fourth segment in the Tipulid Crane Fly.
Tipulid Crane flies are more likely to have a pronounced rostrum ("snout") while the Limoniids usually have a rostrum that is not very impressive.
The two families do have features in common, of course, sharing as they do the common name Crane Flies. The most obvious shared trait is the long, thin legs. Everything about these flies is long, in fact: the legs, the wings, the antennae, the abdomens. Other shared traits are more evident with a hand lens or an enlarged photograph. In the image below, note the "V" shaped suture on the dorsal surface of the thorax (on some species the suture looks more like a "U"). On the top of the fly's head, note the absence of ocelli, an absence that is shared by the Tipulid, Limoniid, and Phantom Crane Fly families but not the Winter Crane Flies.
Above: traits shared by Tipulid and Limoniid Crane Flies:
V-shaped suture and a lack of ocelli
Also, long halteres, common to both families
Insects of West Virginia