HABITS, ETC., OF HYLEMYIA GRISEA, FALL. 15 



sineles out a laden bee in order to follow her closely while 

 she flits over the bank, or hesitates a little on the ground, 

 before disappearing within her own burrow to deposit her 

 stores. The fly now takes up a position outside the entrance 

 and facing it, and all the time the bee remains underground 

 unlading and adding the fresh pollen to her ball of nutritive 

 paste — a proceeding which consumes fifteen or twenty 

 minutes — the fly remains motionless. Presently the bee 

 appears at the entrance of her burrow, pausing there before 

 again taking flight in search of further supplies. The fly 

 may betray her eagerness by a forward step or two. A 

 minute or so more and the bee has flown. The fly now darts 

 into the burrow, examines the passage for a second or two, 

 comes out again and re-enters backwards in order to lay an 

 egg on the floor of the burrow, not more than half an inch 

 from its entrance. This is accomplished usually in less than 

 a minute, and the fly has gone long before the return of the 

 bee. From a favourable position one need not lose sight of 

 the ovipositing fly, and the egg can be obtained by lifting 

 the sand from the spot on the blade of a pocket-knife. 

 Should the bee not come out again, as often happened owing 

 to the departure of the sunshine, the patience of the fly 

 becomes in time exhausted and she moves away. At times 

 bees will return to the sandbank bearing no pollen. The 

 flies will spontaneously rise to greet them, but perceiving 

 the absence of the pollen load they make no pursuit. 



This then is the state of matters in July : — A dipterous 

 maggot in the bee's nest and a fly laying eggs at the entrance. 

 Two questions naturally suggest themselves. Is the maggot 

 the offspring of the fly ; and if so, how is the egg taken down 

 to the nest ? 



Many burrows were investigated and brood chambers 

 containing fly m.aggots in the act of devouring the pollen ball 

 were again and again found. Sometimes the chamber was 

 removed almost intact so that the maggot suffered little 

 disturbance and continued to eat the pollen while watched 

 under a lens, but light proved unpleasant to these larvae, and 

 a few minutes' exposure to it caused them to stop eating and 

 to seek darkness Placed in small tin boxes containing sand, 



