Contributions toward a revision of the genus Atrichopogon based on characters of all stages (Diptera, Heleidae)

Abstract

Atrichopogon is a large genus in the subfamily Forcipomyinae of the family Heleidae (= Ceratopogonidae). Systematists have experienced difficulty in identifying species and in splitting the genus into manageable subgenera on the basis of adult characters. Thus in 1913 Kieffer erected the genus Kempia to include those forms which have pubescent eyes and this is still recognized as a subgenus of Atrichopogon by some authors. However, this character is so variable that it is unworkable, some species having the eyes pubescent only above, others only below (Wirth, 1952). Similarily Kieffer’s Gymnohelea, based on species which have lost all the macrotrichia, of the wings, cannot be maintained (Edwards, 1926). Wirth’s subgenus Meloehelea, based on species which parasitize meloid beetles and have an unusually upcurved proboscis, can still be maintained although the immature stages of only one species, A. (Meloehelea) meloesugans (Kieffer), are known. Only the description of the early stages of more species will confirm the validity of this subgenus. As pointed out by Edwards (1926), Nielsen (1951) and Wirth (1952), the imagines of the genus Atrichopogon are very difficult to separate, offering no good, clear-cut character, or even combination of characters. The characters that have been used are color, proportions of antenna or tarsal segments, and hairiness of wing or scutellum, all of which exhibit great individual variation. In view of these difficulties we are "in the peculiar situation to be forced to base the taxonomy to a great extent upon the developmental instars" (Nielsen, 1951). The name Atrichopogon itself is mystifying, for it indicates an impossible situation: a beard ("pogon") without ("a") hairs ("tricho"). All species discussed in this work are from reared larvae. The bulk of the material was collected by Dr. L. G. Saunders in many countries over many years. Five species were taken in localities around Saskatoon, Canada. Except for A. minutes (Meigen), A. polydactylus Nielsen, A. fuscua (Meigen) and A. (Meloehelea) meloesugans (Kieffer), my endeavours to identify the species failed to find full agreement with any existing descriptions. Hence, each species studied, except for those mentioned above, has been given a new name. I prefer to run the risk of creating a new synonym rather than refer the larva and pupa to the wrong species. The species are not treated in any special order. Especially, there is no phylogenetic significance to the sequence.