16 
equally well to the above-named insects. One ounce per square yard 
divided among three or four injections should give very satisfactory 
results. The life cycle of these insects occupies three years. The 
eggs are laid about June, and the young larve feed very close to the 
surface until cold weather comes on, then all go down to a considerable 
depth to spend the winter. The most favorable time for the treat- 
ment of these pests is after they descend in the fall and before they 
come up again in the spring. If treatment is made in midsummer, 
many of the small insects are so near the surface that they will escape, 
owing to the ready dilution of the vapors by the air. If the soil is 
fairly permeable and at least 8 inches in depth, a careful treatment 
should be successful and the ravages of the insects for three years will 
be prevented by one operation. 
OTHER SUBTERRANEAN USES. 
The vapor of carbon bisulphid applied at the rates previously recom- 
mended is said to have a marked action against certain cryptogamic 
parasites of plants, though its influence in this direction does not appear 
to have been much studied. It is also said to be fatal to the nematode 
worms, which are frequently injurious. In greenhouses these would 
seem to be particularly susceptible to effective treatment. The vapor 
of carbon bisulphid is fatal to animal life of all forms if inhaled in 
sufficient quantity. Within recent years this chemical has come into 
quite.extensive and successful use against a class of small mammals 
which are common nuisances, if not actual pests, in many parts of the 
country, and particularly in the West. To Prof. E. W. Hilgard, of the 
University of California, is given the credit of being the first to employ 
this remedy against ground squirrels and gophers.’ It is a matter of 
common knowledge that this agent is by far the safest and most efficient 
known for the destruction of prairie dogs, gophers, pocket gophers, 
ground squirrels, woodchucks, moles, and other pests having similar 
burrowing habits. The subject is quite an extensive one, and as it is 
now being given consideration by the Division of Biological Survey, 
and does not properly come within the province of the Division of 
Entomology, further comments here are unnecessary. 
DESTROYING BORERS IN TRUNES OF TREES. 
Considerable has been written in favor of this use of carbon bisul- 
phid. It is apparent that only the large borers which work in the 
trunks and lower branches of trees will be good subjects for this treat- 
ment. There are usually but few of these in each trunk, and the out- 
lets of such burrows as contain active borers are usually marked by 
the sawdust and castings which the borers throw out therefrom. 
1Bul. 32, Uniy. Cal., ‘‘On the Destruction of the Ground Squirrel by the use of 
Bisulphide of Carbon,’’ 1878. 
