AND COLLEGE, PUSA, FOR 191.5-16 7< 



II. Work done. Disease-carrying insects. 



Cattle Flies. 



Observations were continued on the life-histories of 

 various Tabanidae occurring at Pusa. As regards the 

 feeding-habits of Tabanid larvae it was noted that canni- 

 balism is not universal; at least, so far as observed, larvse 

 of Tabanus nemocallosus do not attack and destroy one 

 another. Forty nearly full-grown larvae of this species 

 were collected and confined in a very small glass vessel, with 

 some moist earth, but actual counts made twice weekly 

 discovered no larvae missing or damaged. Of these larvae, 

 collected on 27th January, only a very few emerged as flies 

 in March, the majority in April and May, and a few in 

 June. The pupal period is eight or nine days. One larva 

 kept under submerged conditions lived for over three 

 months in water without any food ; these larvae must there- 

 fore have a respiratory system fitted for both aquatic and 

 terrestrial life and can exist over a considerable period it 

 conditions are unfavourable. Egg-masses of T. nemo- 

 callosus were found fairly commonly from the third week 

 in April ; this species appears to be rather gregarious in its 

 egg-laying habits, depositing its egg-masses by preference 

 on Phragmites. The newly hatched larvae are also gregari- 

 ous in habit, often noted to be crowded up in a mass in one 

 place in the breeding vessel. Grown larvae are also more or 

 less gregarious, as on one occasion 63 grown larvae were col- 

 lected in one small area of about two square yards, such den- 

 sity of population being only possible if a non-cannibalistic 

 habit is usual. As regards the feeding habits of the adult 

 flies of Tabanus nemocallosus it was found that when bred 

 females, starved under humid conditions for twenty-four 

 hours after emergence from pupa, were allowed to bite, 

 under cover of a test-tube, a goat whose skin had been 

 shaven and moistened a little before they were placed to 

 feed, all of them were observed to suck blood within five 

 minutes; in the case of other Tabanids, various observers 



