FAMILY TABAXIDJ-: — THE HORSE FLIES 149 



subfamily contains some of the most serious pests of man. The males 

 of some species feed upon pollen and nectar and may be found upon 

 most melliferous flowers, hovering over streams or pools or even along 

 paths. The sexes are frequently very diiferent in appearance and diffi- 

 cult to associate. 



The transmittal of disease by Tabanids may be a purely mechanical 

 operation or the flies may serve as intermediate hosts of the parasitic 

 organisms causing disease. Tularemia is spread mechanically and is 

 transmitted by CJirysops discaUs Williston. Normally it is a disease 

 of rodents (particularly rabbits) but man sometimes develops the dis- 

 ease after being bitten by the fly. It has also been demonstrated that 

 Anthrax may be carried on the proboscis of Tabanids and cause infec- 

 tion as a result of the bite of the fly and various species of trypanosomes 

 are transmitted. In Africa a filarial disease caused by Loa loa Cobbald, 

 and known by that name, is transmitted by two species of Chrijsops. 

 The details have been worked out by A. and S. A. Connal (Trans. 

 Roy. Soc. Trop. Med. Hyg., xv, pp. 131-134, 1913). 



The eggs are laid, as a rule, in large masses on leaves and stems 

 of ])lants overhanging water and are usually brown or black in color. 

 They show characteristic generic arrangement and sometimes specific 

 characters but too little is known about them to permit of their identifi- 

 cation. The larvae are predaceous. Larvse have been found in rotten 

 wood, under stones, in mud, etc. Pu])ation takes places near the surface 

 of the soil. There are many papers dealing with the biology of North 

 American Tabanidip, l)ut most of them are quite short. Papers by 

 Cameron* and ]\Iarchandt on the immature stages are the most com- 

 l)rehensive. 



The numlxn- of species of TabanidiO is large, the genus I'ahann.-i 

 alone containing about 1200 described species. The first (and only) 

 North American monograph of the family was published by Osten 

 Sacken in 1875 and 1878. Since that time the number of species has 

 greatly increased and the difficulty of identifying specimens is relatively 

 greater. Hine has published on the Tabanida? of Ohioi, while there are 

 numerous short papers scattered through the literature. 



Fascicle 175 of "Genera Insectorum", by Dr. J. Surcouf, deals 

 with this family but the treatment has been rather unfavorably 

 criticized by other workers in the field. Several American students are 

 now studying the family and excellent revisions of the nearctic species 

 may be expected to appear in the near future. 



* Cameron. 1926, Bull. Ent. Res., xvii, pp. 1-42, 5 plates. 



t Marchand. 1920. Mon. Rockefeller Inst. Med. Res., No. 13, w. 1-203, 15 plates. 



t Hine, 1903, Ohio State University Bulletin, Ser. 7, No. 19. 



