f 



BIOLOGY AND HABITS OF HORSE FLIES 243 



larvjE by digging in dry ground along the borders of ponds. He also 

 states that the larvae of Tabanus atratus Fabricius are sometimes found in 

 rotten logs. It is probable that Hine uses the term "dry ground" in a 

 comparative sense, and that both the dry ground referred to and the 

 rotten logs contained some degree of moisture. 



The length of the larval period varies greatly in different species, and 

 even among different individuals of the same species. The shortest periods 

 for this stage are found, as might be expected, in tlie tropics. Thus, 

 Mitzmain records a minimum larval period of 9 days for Tabanus striatus 

 in the Pliilippines. The maximum period is given for this species as 3 

 months. Neave gives the larval period for Nyasaland Tabanids as 6 

 months or more. 



In Ohio, Hine found in rearing Tabanus lasiophthalmus Macquart 

 under laboratory conditions that in one instance the larval period was 

 from June 30 to March 10, approximately 8^ months. In the case of 

 the species which I have been studying in the Sierra Nevada Mountains, 

 the larval periods have not yet been determined, but all signs point to 

 periods extending over two winters. As a matter of fact, data on the 

 larval periods of species of Tabanus are verv meager. 



When the time for pupation arrives, the larva usually seeks drier 

 quarters, though some moisture is usually necessary to maintain life 

 during this period. Larvae living in the mud of stream beds usually work 

 their way to the drier soil of the stream banks in preparation for pupa- 

 tion. Pupae of most species are much more difficult to locate in nature than 

 larvae. The length of the pupal period is usually comparatively short. 

 Mitzmain gives the period for Tabanus striatus in the Philippines as from 

 3 to 7 daj^s, while King records that of Tabanus par in the Anglo- 

 Egyptian Sudan as 6 to 8 days. Neave states that this period in Nyasa- 

 land Tabanids varies from 10 to 16 or 18 days. In rearing Tabanus 

 lasiophthalmus in Ohio, Hine found the pupal period to be 15 days. 



My records show that under laboratory conditions in the Sierra 

 Nevada Mountains this period m Tabanus phaenops is from 14 to 22 

 days, while that of Tabanus punctifer (plate XX, fig. 3) is 27 to 28 days. 



LIFE CYCLE 



The shortest life cycle from egg deposition to emergence of adult, 

 which I find recorded, is 48 days, in the case of Tabanus ditaeniatus in 

 the Anglo-Egyptian Sudan. King gives the life cycle as 48 to 131 days. 



