E. Hargkeavks 331 



specimen tube over u i\y, touch it with tlie edge of the tube. It may 

 behave in two ways : either it flies immediately upwards into the tube, 

 or it simply falls over on its side feigning death. If a fly is touched while 

 the leaf is in the normal position, it does not generally immediately 

 take to flight, but drops for three or four inches, and then flies quickly 

 away from the plant. If a number of the flies are placed in a tube, 

 they all congregate at the upper end. This seems to be an attempt to 

 get into the position with the dorsal surface downwards, and not a result 

 of photo tropism. I placed some flies in a tube, and, as usual, they 

 congregated at the upper end. So I covered all the tube except the 

 lower part to exclude the light, and placed a Nernst lamp beneath, so 

 that the light was shining upwards into the darkened tube. It did not, 

 however, cause the flies to come to the bottom of the tube, which 

 indicates that they are not positively photo tropic. And their general 

 behaviour points to their not being negatively phototropic. 



(5) I consider that the situation of all the stages on the under leaf- 

 surface is correlated with the dorsal position of the anus. The following 

 considerations lead me to this conclusion: 



If the insect were dorsal surface upwards 



(a) it would be unable to get rid of its excreta, which would clog 

 the anus, or, accumulating on the leaf and becoming viscous, would 

 occlude the spiracles, 



(6) any accumulation of honeydew (excreta) is a very suitable 

 medium for the growth of Fungi, 



(c) the newly-hatched first larva would become entangled in the 

 viscous excreta which fouled the leaf and would be unable to settle 

 down, 



{d) the various larvae when moulting would have difficulty in 

 casting off their old skins. 



Enemies. Now as to the enemies of the insect. I have not en- 

 countered any animal parasites as yet, either of the nymphs or the adult. 

 On one occasion I caught a mite which was holding and devouring 

 a living fly. Spiders also prey on them. On one leaf a spider was 

 discovered surrounded by the remains of half-a-dozen of the flies. 

 Fungi occasionally kill both adults and nymphs. 



MetJwds of eluding jyredaceous enemies. (1) Escape by dropping, 

 and flight. 



(2) Transparency of the larvae is probably a factor in this, as it 

 renders them practically invisible. 



