322 Annual Report for 1908 of the Zoologist. 
.very small size of the insect has something to do with it, for 
it is difficult to credit it with the powers of destruction it 
really possesses. Probably the failure it causes has generally 
been put down to obscure weather influences, or in some cases 
to a fungus attack, especially as a fungoid disease is often 
found associated with it ; but that it is really destructive in 
itself any member may very readily convince himself by the 
inspection of a few vegetable gardens next season, when once 
the nature of the attack has been pointed out. 
Appearance of the disease . — The disease is recognised by 
the blighted and distorted appearance of the developing pods, 
which, instead of being uniformly green and straight, are 
marked with white and straw-coloured blotches and curled to 
one side. Closer examination shows them to be infested by 
numbers of small yellow maggot-like creatures. There is no 
Fig. 1. — The Pea Thrips. The winged, female ( somewhat too broad, owing to 
compression) and the larva, both greatly magnified. The natural size is indicated in 
each case. 
absolute destruction of tissue ; if the leaves are perforated or 
eaten away, this is due to some other pest, but the general 
effect is a very unhealthy appearance. 
To understand exactly what has happened, it is necessary 
to study the structure of the pea-flower and see how the pod 
arises. In the very centre of the flower will be found the 
ovary, or future pod, enveloped in a sheath, from which spring 
the stamens. Next comes the corolla of white petals, con- 
sisting of a large upper petal or “ standard,” two side petals or 
“ wings ” (with dark patches on them) and two lower petals 
fused together to form a “ keel.” Outside this is the little 
five-pointed green calyx. Very soon after fertilisation has 
taken place, the standard and the wings fall away, and the 
ovary begins to develop into the pod, generally carrying with 
