ENTOMOLOGY

BIOLOGY AND HABITS OF HORSE FLIES !43larvre by digging in dry groun,d along the borders of ponds. He alsostates that the l.arvre of Tabanus atratus Fabricius are sometimes found inrotten logs. It is probable that Hine uses the term "dry ground" in acomparative sense, and that both the dry ground referred to and therotten logs contained some degree of moisture.The length of the larval period variee greatly in different species, andeven among different individuals of the same species. The shortest periodsfor this stage are found, as might be expected, in the tropics. Thus,Mitzmain records a minimum larval period of 9 days for TabanU8 striatU8in the Philippines. The maximum period is given for this species as Smonths. Neave gives the larval period for Nyasaland Tabanids as 6months or more.In Ohio, Hine found in rearing Tabanus lasiophtholm'US Macquartunder laboratory conditions that in one instance the larval period wasfrom June 30 to March 10, approximately 8lA! months. In the case ofthe species which I have been studying in the Sierra Nevada Mountains,the larval periods have not yet been detel'fIlined, but all signs point toperiods extending over two winters. As a matter of fact, data on thelarval periods of species of Tabanus are verv meager.l'UP&When the time for pupation arrives, the larva usually seeks drierquarters, though some moisture is usually necessary to maintain lifeduring this period. Larvre living in the mud of stream beds usually worktheir way to the drier soil of the stream banks in preparation fo'r pupation.Pupre of most species are much more difficult to locate in nature thanlarvre. The length of the pupal period is usually comparatively short.Mitzmain gives the period for TabOlT1llJ,s striat'US in the Philippines as fromS to 7 days, while IGng records that of Tabanus par in the Anglo­Egyptian Sudan as 6 to 8 days. Neave states that this period in NyasalandTabanids varies from 10 to 16 or 18 days. In rearing Tabanuslasiophthalm'US in Ohio, Hine found the pupal period to be 15 days.My records show that under laboratory conditions in the SierraNevada Mountains this period In Tabanrts phaenops is from 14 to 22days, while that of TabanU8 pwnctifer (plate XX, fig. S) is 27 to 28 days.LIFE CYCLEThe shortest life cycle from egg deposition to emergence of adult,which I find recorded, is 48 days, in the case of Tabanus ditaeniatU8 inthe Anglo-Egyptian Sudan. King gives the life cycle as 48 to lSI days.