blood for several minutes. When they have finished feeding, blood usually oozes from the punctures they 

 have made in the skin. At times, the Amount of blood lost in this manner by some animals is devitalizing. 



Most of the horse flies found in Illinois belong to the genus Tabanus , and for that reason they are 

 sometimes referred to as tabanids. The largest of these flies, and the one that does the most harm in 

 southern Illinois, is called Tabanus sulcifrons Macquart. The male is almost an inch long and the female 

 somewhat longer. Both are reddish-brown in color except for a row of white or yellowish triangles down 

 the middle of the abdomen. 



Like other horse flies, this large tabanid passes the winter as a nearly full-grown larva in mud, 

 often near lakes or streams, in damp woods or marshy pastures. As it nears maturity, it wriggles to a 

 drier spot, passes through a pupal stage, and in late spring or early summer emerges as a winged adult. 

 The female feeds on blood of cattle and other animals, the male on nectar, honeydew, soft fruits, and simi- 

 lar substances. The female lays her eggs usually on plants or other objects close to water. In about a 

 week, small maggots hatch from the eggs, drop into the water, and bury themselves in the soil at the bot- 

 tom, where they feed on such small animals as insects and earthworms. 



HORSE FLY CONTROL ON DAIRY CATTLE 



Until very recently, no effective controls for horse flies were known. Even DDT, the miracle in- 

 secticide, proved ineffectual against blood-thirsty tabanids. 



In the summer of 1947, the Illinois Natural History Survey began a systematic search for an insec- 

 ticide that would control horse flies under southern Illinois conditions. Of the large number of materials 

 tested, activated pyrethrins gave the best results. Repeated tests made the following year showed that 

 cattle could be protected from horse flies by frequent sprayings (3 to 5 days apart) with an emulsion con- 

 taining 0.125 per cent pyrethrins and 2.5 per cent piperonyl butoxide. 



Further experiments were set up in 1949 to discover how a maximum amount of protection could be 

 obtained with minimum cost and effort. Because of the necessary frequency of treatment, tests were con- 

 fined to dairy animals that could be conveniently treated at least twice a week. 



Twelve herds of dairy cows were divided into six groups of two herds each. Cows in three of the 

 groups were sprayed with hand -power sprayers in which undiluted Pjrrenone T-143 (1.0 per cent pjrreth- 

 rins and 10.0 per cent piperonyl butoxide) was used; cows in the first of these three groups were sprayed 

 twice daily, each time with 1 to 2 milliliters per animal; those in the second, once daily with 2 to 5 milli- 

 liters per animal; and those in the third, twice weekly with 22 to 39 milliliters per animal per treatment. 

 Cows in the other three groups were sprayed with a knapsack compressed-air sprayer in which 1 part of 



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