Annual Report for 1913 of the Zoologist . $83 
since shewn. The eggs develop inside the substance of the 
stamen sheath and the larvae presently emerge and attack the 
underlying ovary, which is now developing to form the pod. 
This they injure, not by devouring its tissue, but by inserting 
their mouth-parts and sucking the sap, and the infested pod 
soon assumes the appearance characteristic of the disease. 
So far the life-history was clear, but a very important point 
remained undetermined. Where did the change from the larva 
to the adult take place and whence came the flies which began 
the annual attack ? Other species of thrips were known to pass 
the winter in the mature form and it was thought probable that 
the pea-thrips did the same. The loose bark of old pea-Sticks, 
heaps of leaf-mould and similar shelters were suspected of 
sheltering them, and the impracticability of dealing satisfac- 
torily with their possible winter quarters made it very difficult 
to suggest any means of preventing the attack. 
Fig. 2. — Pea-thrips’ larva enlarged. 
But from the investigations of Mr. Williams it appears almost 
certain that this particular thrips does not pass the winter as a 
mature insect, but remains as a larva in the soil till the spring, 
delaying its final changes until the following May, when the flies 
emerge and find material at hand in the shape of the developing 
pea blossoms. 
It follows, therefore, that the soil in which the peas we^e 
grown must be treated in some way to prevent an attack next 
year, and that instead of searching for possible shelters for the 
hibernating fly we ought to dress the ground, immediately after 
the crop is gathered, with some preparation likely to kill the 
larva which have dropped from the pods fully fed and purpose 
remaining in the soil till the following spring. The forking in 
of lime and soot or vaporite, or the injection of carbon 
bisulphide, or the application of any of the numerous prepara- 
tions suitable for the destruction of underground insects ought 
