ENTOMOLOGY 849 
SIMULIIDAE 
The Simuliidae, known in the vernacular as black-flies or buffalo-gnats, are 
of almost world-wide distribution, since they extend from the equator to near the 
Arctic circle and are found from sea-level to an altitude of at least 9,000 ft. 
Some 330 species have been described to date, divided among the several z06- 
geographical regions as follows: 125 Palaearctic, 53 Nearctic, 80 Neotropical, 24 
Ethiopian (including 5 species from the Malagasy Subregion), 26 Oriental, and 
24 Australasian. The females alone bite and, as they often occur in extraordi- 
nary numbers, they are in spite of the small size among the worst insect pests 
in many parts of the world. It is probable that their réle as carriers of contagious 
diseases and parasites is more important than realized. At present, however, it 
has been demonstrated beyond doubt in one case only, viz., for the African para- 
sitic worm of man, Onchocerca volvulus (Leuckart). 
In various countries, even outside the tropics, black-flies may become so 
numerous at certain seasons, that they render those regions uninhabitable for 
man and beast alike. Their attacks are the more dreaded because they often 
induce severe symptoms or are even followed by death. The notorious Golubatz 
fly of eastern Central Europe, Simuliwm columbaczense (Schénbauer), causes 
every year severe losses in domestic animals. The bite of some other European 
species also appears to be dangerous at times. Years ago, swarms of a North 
American species, Husimulium pecuarum (Riley), used to cause the death of 
cattle and horses in the lower Mississippi Valley.!. According to Dyar and 
Shannon (1927, Proc. U. S. Nat. Mus., LXIX, Art. 10, p. 19), no serious out- 
breaks have occurred during the past thirty to forty years. Another species, 
Simulium occidentale Townsend (S. meridionale of authors), known as the 
‘cholera gnat”’ or ‘‘turkey gnat,” is widely distributed in the United States. 
In former years (about 1888) it was claimed to cause the death of chickens and 
turkeys, producing symptoms similar to cholera (Dyar and Shannon, 1927, loc. 
cit., p. 33). Recently G. P. Walker has reported that, in Nova Scotia and New 
Brunswick, large numbers of Husimuliwm aureum var. bracteatum (Coquillett) 
bite geese and ducks preferably to man. He believes that in one case the bites 
were responsible for the death of young geese.’ 
The grave symptoms or death that sometimes follow the bite of black-flies 
appear to be due to a toxic substance secreted by the flies and injected into the 
blood and tissues of the animals. At any rate, no specific germ has thus far 
been found associated with these morbid conditions. The exact nature of the 
poison is as yet unknown. Most animals seem to become immune to the poison 
when they are gradually exposed to the bites of the black-flies. According to 
Wilhelmi’s ‘‘climatic and immunity theory,” the Simuliidae become dangerous 
only when they hatch in enormous numbers following sudden rises of the 
1 Riley, C. V. 1885. ‘The southern buffalo gnat (Szmuliwm sp.).’ Rept. Entomologist U. S. Dept. 
Agric. for 1884, pp. 340-345. 
1887. ‘Report of the Entomologist.’ Rept. U.S. Comm. Agric. for 1886, pp. 459-592, Pls. I-XI. 
2 Walker, G. P. 1927. ‘A black-fly (Simuliwm bracteatum) fatal to goslings.’ Canad. Entom., LIX, 
p. 123. 
