Annual Report for 1908 of the Zoologist. 327 
of sucking insects, but they were tried, with no very beneficial 
result. In some varieties of pea, moreover, the pods would 
not receive a uniform deposit of the spray and remained largely 
unaffected by it. 
Distinct improvement, however, resulted from topping the 
plants, just as beans are topped when suffering from aphis. 
The topmost shoots seemed to be the main seat of the attack, 
and the disease was certainly mitigated by their removal. In 
some cases badly diseased plants so treated put forth a late 
crop of perfectly clean pods. 
“Leather Jackets” or Crane Fly Grubs. 
The problem of dealing with root-feeding pests in grass 
land is always cropping up. Any really drastic measures are 
precluded, or grass land ceases to be such, so that more or 
less indirect methods of treatment have to be resorted to. 
With the assistance of Mr. F. W. Foreman I undertook 
some experiments in September last, the results of which it is 
as well to record though they were mainly negative. Their 
object was twofold : — 
(a) To determine if any treatment would kill the grubs 
without injuring the grass. 
( b ) To see if by any means the grubs could be induced to 
come to the surface so that they might be collected and killed. 
A variety of compounds were experimented with, including 
the vapours of hydrocyanic acid and carbon bisulphide, and 
solutions of formalin, ammonia, carbolic acid, toluene, and 
other substances. 
A large number of “ leather-jackets ” were obtained and 
the direct effect upon some of them of the various insecticides 
was observed. Others were introduced into an enclosed plot of 
grass land, cut off .from the neighbouring ground by a sheet- 
iron fence sunk some inches into the soil. 
Hydrocyanic ( Prussic ) acid . — As the cases immediately 
under consideration concerned certain circumscribed areas — 
the putting greens of golf links — it seemed worth while to 
try whether the vapour of hydrocyanic acid could be made 
to permeate the soil and kill the grubs underground. In 
orcfer, therefore, to determine whether sufficient diffusion of 
the gas would take place to have an effect at any considerable 
distance, generating tubes were buried, and other tubes 
containing potassium nitrate were also inserted into the 
ground some distance away. If the vapour reached them in 
the soil, they would, on analysis, show traces of its presence. 
No such traces were found. The soil was somewhat heavy, 
and therefore more unfavourable to diffusion than many, but 
the experiment was not encouraging. 
