Family Blephariceridae - Net-winged Midges

Blephariceridae Loew 1861

40 spp. in 4 genera in our area (all members of Blepharicerinae)(1)(2)(3), ~330 described spp. in ~40 genera of 2 subfamilies worldwide(4); in some NA streams up to 10 spp. are known to co-occur(2)

3-13 mm(5)

Adults can be easily recognized by the network of numerous delicate cracks and folds in wing membrane, and by distinctive resting position, with the wings held at a moderate angle to the body and the hindlegs angled at the tibiofemoral joint. Larvae distinctive, with adaptations to a life in flowing water, including a cephalothorax (fused head, thorax and first abdominal segment) and six ventral suctorial discs: body appears to consist of only 6-7 segments (each bearing a ventral sucker) separated by deep constrictions. Pupae are oval, with flat, soft ventral face cemented to rocks.(6)

Keys to larvae, pupae & adults in(7)(1)(2)

In our area, mostly western(1), only Blepharicera are widespread(8); globally, represented on all continents except Antarctica, and on several large islands, with high regional endemism; Blepharicerinae occur in both hemispheres, Edwardsininae are restricted to the southern hemisphere(7)

Larvae live in clean, cool, well-oxygenated rapid streams (cascades, rapids, waterfalls) attached by ventral suckers to rocks or other smooth hard substrata; prepupal larvae often migrate to specific areas of the rock or stream. Adults usually stay in the riparian zone; Blepharicera are often seen resting on the undersides of leaves of riparian trees, while many Agathon and Philorus spp. prefer to rest on wet overhanging rock faces.(7)(6)(5)

Larvae are highly specialized scrapers, grazing on microscopic growths (=periphyton) and other organic matter on submerged rocks; diatoms appear to be a major component of their diet(9)(10). Females of many species are predators of other insects, esp. soft-bodied ones (mayflies, stoneflies, sometimes other Diptera)(2), caught with specialized hind tarsi. The food of males and nonmandibulate females is unknown, but nectarivory is likely in some species.(7)(6)

Four larval instars. Adults of most spp., esp. the males, are short-lived. Mating typically occurs soon after emergence and oviposition shortly after copulation. Small clusters of eggs are cemented to wetted or emergent rocks. In some species, the female crawls underwater on submerged rocks to lay eggs.(7)(2)

Although often considered rare, densities of immature stages can exceed 1000/m², so in some spots blepharicerids both are the dominant grazers and the most abundant insects.(2) They may be a valuable bioindicator of water quality and sometimes an important food for trout.(11)

Courtney, G.W. (2000) Revision of the net-winged midges of the genus Blepharicera Macquart (Diptera: Blephariceridae) of eastern North America. Memoirs of the Entomological Society of Washington, 23, 1–99. (Full Text)

Gibo, D. L. (1964). Notes on the Biology of Blepharocera micheneri and Philorus yosemite (Diptera: Blepharoceridae) in Southern California. Bull. So. Calif. Acad. Sci. 63:44-53. (Full Text)

Hogue, C.L. (1966). The California species of Philorus: Taxonomy, early stages and descriptions of two new species. L. A. County Mus. Cont. Sci. 99:l-22.(Full Text)

Hogue, C.L. (1973). The net-winged midges or Blephariceridae of California. California Insect Survey, Bulletin 15:1-83. (Full Text)

Hogue, C.L. (1978). The net-winged midges of eastern North America, with notes on new taxonomic characters in the family Blephariceridae (Diptera). L. A. County Mus. Contr. Sci.291: 1-41. (Full Text)

Kellogg, V.L. (1903). The net-winged midges (Blepharoceridae) of North America. Proc. Cal. Acad. Sci., Ser. 3 3:187-221. (Full Text)

Pommen, G.D.W. & D.A. Craig (1995). Flow patterns around gills of pupal net-winged midges (Diptera: Blephariceridae): possible implications for respiration. Can. J. Zool. 73: 373-382. (Full Text)