104 First Report on Economic Zoology . 
especially where as in grass land we have absolutely no means of 
controlling them. The extra cost of night work would be amply 
repaid. It is recorded by Miss Ormerod “ that the grubs may be 
collected by a top dressing of rape-cake and the roller passed over 
the ground in the morning with good results ” ; this does not always 
seem to have the desired effect, however. 
Traps may be employed in gardens in the form of heaps of turf, 
partly buried in the soil ; the flies lay their eggs there and the larvae 
seem to be attracted to it and can then be collected and killed. 
Hotting turf-manure and leaf-mould heaps should be kept free from 
surface weeds and top dressed with gas lime, or else they will form 
breeding grounds for these Tipulidae, and the larvae will be carried 
to field and garden, and so contaminate the soil. Grass-borders in 
gardens are favourite breeding grounds, and from these the larvae 
spread to the bedding plants. In garden borders and beds they can 
be easily destroyed by injecting bisulphide of carbon into the soil at 
the rate of half an ounce to every square yard. This should be done 
in late autumn or early spring. When crops are attacked various 
stimulating manures should be employed ; they do not kill the larvae, 
but they hasten on the growth of the plant and repair some of the 
damage that the grubs have done. Nitrate of soda has the greatest 
effect upon leather-jackets, but is not permanent in its action. It, 
however, causes a cachectic condition in these pests, from which they 
do not recover for some days, if its application at the rate of 2^ cwt. to 
the acre is followed by rain. Miss Ormerod records an experiment 
in which at the rate of 2 cwt. to the acre they had not recovered 
from its ill effects after eight days. The effect of this artificial 
manure on insects is so extremely variable that one must not rely on 
it too much. At the same time it must be borne in mind that if it 
has not the desired effect on the grub, it is still of value as a 
stimulant to the plant. Hand and horse hoeing have also been 
recommended and largely followed, but the good done is scarcely 
sufficient for the outlay. 
