28 THE EARLY STAGES OF TABANID^ 



larval stage, the pupal period is short, varying, in Neave's experience, 

 from 10 to 16 or 18 days, according to the species and the climatic 

 conditions, the longer period being usual for the larger species of 

 Tabanus. 



One difficulty connected with the question of these flies having 

 more than one brood a year arises from the fact that even in larvae 

 from the same batch of eggs the rate of growth is extremely variable, 

 and consequently the processes of pupation and emergence do not take 

 place simultaneously in a certain proportion of the individuals. Some 

 of the remainder take longer to reach maturity, others seem to pass 

 through an extended dormant period. The adults arising from these 

 emerge at irregular intervals, often months later. This probably 

 explains the capture of odd specimens of any species long after the 

 usual season. It would also seem not improbable that individuals 

 which miss their normal season for pupation in some circumstances 

 continue in the larval stage until the following year. Thus Neave 

 possessed in his laboratory in January and February examples of 

 larvae of Tabanus corax, some still in a dormant state and others not 

 yet mature, the season for the adult flies being over by the begin- 

 ning of January. It would appear that these would not have pro- 

 duced imagos until the following December, though Neave was un- 

 able to decide this point on account of his return from Nyasaland to 

 England. Hine states that the larvae of Tabanus stygius — probably — 

 hibernate twice before giving the adult. 



Surcouf and Ricardo, however, assert that in spite of the opinions 

 to the contrary the tabanids seem to have, at least in Algiers, often 

 two generations in a year. These authors have taken from a horse 

 several fresh specimens in May (1908), while the same species is taken 

 in France and Algiers in the fall. Maxwell-Leffroy and Howlett state 

 that at Pusa (Bengal) there are apparently three broods of Tabanus 

 yearly, flies emerging at the beginning and end of the hot weather 

 (about February and June) and at the end of the rains (October). 

 These statements should be compared with those made by Neave. 

 Hibernation takes place in the larval state in India in all species 

 which were observed by Maxwell-Leffroy and Howlett; and the same 

 holds good for all known American species (Hine) , larvae being found 

 late in the fall and again in early spring. No pupae have been found 

 in the winter. 



