359 



occur commonly. Some success in destroying the flies has been at- 

 tained by spreading a film of kerosene on the surface of pools where 

 the insects occur. The flies have a peculiar habit of dipping down to 

 the surface of the water, assumably for the purpose of drinking, and 

 when the oil is present large numbers are destroyed. Various skin 

 lotions, or washes, consisting of lard and sulphur or of carbolic acid 

 in varying strength, have been tried as repellents, but usually with 

 very little success. Even hogs that are regularly washed with various 

 crude-oil preparations to destroy lice are attacked freely by such 

 species as atratus. 



Some of the larger asilids, or robber-flies, prey upon the adults 

 and succeed in killing even the largest of them. 



Keys to Species 

 larvae 



1. Body without markings either of color or hairs 2 



Body either with a series of distinct brown spots or with brown 



marks 3 



2. Body very closely and finely striated, entirely white. Tab an us sp. 1. 



— Body coarsely striate, abdominal segments each with an indistinct 



pale annulus on anterior margin costalis. 



3. Abdominal segments with very faint anterior annuli costalis. 



— Abdominal segments cither with very well-defined anterior annuli 



or each segment with a brown spot on each side on extremity of 

 dorsal transverse swelling 4 



4. Brown markings consisting of a small spot on the outer extremity 



of each dorsal abdominal transverse swelling Tabanus sp. 2. 



— • Brown markings in the form of well-defined annuli 5 



5. Lateral raised striated areas of prothorax each about as long as the 



dorsal one lineola. 



— Lateral raised striated areas of prothorax each about half as long as 



dorsal one 6 



6. Brown stripe between dorsal striated area and upper lateral one 



dilated posteriorly, causing the former to be parallel-sided on its 

 posterior half (PI. LI, Fig. 3) atratus. 



— Brown stripe between dorsal striated area and upper lateral one 



tapered, or at least not dilated, posteriorly, the sides of the dorsal 

 area divergent throughout their entire length (PI. LI, Fig. 2) . .7 



7. Lateral striae of prothorax very fine, opaque, those of metathorax 



much coarser, shining Tabanus sp. 3. 



— Lateral striae of prothorax but little finer than those of meso- 



thorax stygius and nign set ns. 



