326 Annual Report for 1908 of the Zoologist. 
before the flowers were developed. At all events the origin of 
the disease of the pods was clear enough. The female must 
crawl into the flower and pierce the stamen-sheath at intervals 
with her ovipositor, depositing an egg at each operation. 
While the larvae are developing, so is the pod, and their future 
feeding ground is close at hand. When they emerge they have 
only to crawl on to the adjacent pod which they pierce with 
their jaws, abstracting the sap and mottling the green surface 
with white patches, at first only at the base, but later at both 
ends where they have convenient shelter if disturbed. The 
pod soon looks unhealthy and becomes distorted. 
Treatment . — It is very evident from the nature of the 
disease that it is most important to notice the commencement 
of the attack and deal with it then. The date when it was 
first observed made this impossible last season so that observa- 
tions of the early stages must be deferred till next year, when 
pea-plants will be kept under observation from their first 
appearance above ground. All that is possible at present is to 
state any facts bearing on the origin of the disease and any 
measures which are useful in mitigating its ill effects. 
Where do the insects come from ? Is the soil where 
diseased peas have been grown a danger to next year’s plants ? 
Now the thrips do not pass the winter in the larval state, 
but as mature insects, which certainly do not live under the 
soil but are found, if at all, in flowers or under the bark of 
trees. During attack I never found the larvae on the roots of 
infested peas, and even if they could live there very few roots 
of the old crop are in the ground at the time the seeds are 
sown in the ordinary course of pea cultivation. It would seem 
that the only possible direct connection between two attacks 
would be in the use of pea-sticks a second time with the thrips 
concealed under the bark. During November I searched for 
them in such situations and found two or three species of 
thrips, but I am not aware that the disease only declares 
itself after sticking. The attacks are probably not directly 
connected at all, but arrive quite from the outside, in which 
case preventive measures would be useless. The insect is 
obviously common and widely distributed, whether or not 
the species is really Thrips cerealium. This point requires 
further investigation, as the larva of that species is described 
as yellow, without any mention of the black terminal segments. 
The best hope lies in the discovery of some treatment which 
shall check it when it first begins to attack the peas. 
On the already diseased plants various washes were tried 
with very slight success. Paraffin emulsions did not reach 
any large proportion of the insects, which were too well 
hidden. Arsenic washes were hardly indicated in the case 
