328 
Annual Report for 1908 of the Zoologist. 
Carbon bisulphide . — “ Leather-jackets ” subjected to the 
fumes in the laboratory were much convulsed and evacuated 
copiously. The following morning they were limp, and 
barely alive. Contact with the fluid killed them. It was 
obvious that the attenuated vapour which it might be possible 
to diffuse in the soil would be of little use. 
Toluene affected the grubs exactly in the same way 
as carbon bisulphide. 
Carbolic acid . — This substance is generally regarded as 
particularly destructive of insect life. Moreover, it was 
found that a weak solution (up to - 5 per cent.) had no visible 
injurious effect on the grass. Unfortunately, however, neither 
had it on the grubs. Leather- jackets immersed in it for 
some time seemed unhurt, and were alive and fairly strong 
the next morning. 
Formalin . — Solutions of '5 per cent, and even -2 per cent, 
discoloured and injured the grass, and further experiments 
with it were discontinued. 
Ammonia. — Leather-jackets have often been alleged to be 
particularly susceptible to the destructive effects of this 
insecticide, from which some good results were anticipated. 
A '5 per cent, solution did not hurt the grass, but an application 
of a 1 per cent, solution discoloured it, and, in addition to 
the fear of permanent injury, there was a danger that the 
more delicate grasses would be killed and the coarser species 
encouraged. Moreover, the direct effects on the grub as 
ascertained in the laboratory were not at all satisfactory. 
Subjected to the vapour of a 1 per cent, solution they were 
only slightly inconvenienced. Immersed in it, they evacuated 
so profusely as to become almost transparent, but they were 
all alive the following morning. 
The above experiments made it quite clear that the grubs 
are remarkably difficult to kill, and that it is highly improbable 
that any substance will be found capable of destroying them 
in the ground without greatly injuring the grass. 
Some of the grubs obtained were sent in situ , in a turf 
enclosed in a square tin box. They were all found on the top 
of the turf when the lid was opened in the morning, and this 
fact suggested the possibility of inducing the leather- jackets in 
infested ground to come up to the surface by covering the 
ground over night. No consistent results were obtained, 
however, nor did copious waterings with any of the insecticides 
experimented with bring them to the surface with any 
uniformity. That they frequently come up and wander about 
on their own account, especially in the early morning, is a fact 
well known, and advantage should always be taken of this 
habit when it is observed. Rolling at such times cannot fail 
