BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 87 
have been available heretofore and measures that will not affect the 
marshes as habitats of wildlife. 
Intensive studies are under way to develop mosquito larvicides that 
are not only more effective but also nontoxic to birds, fishes, and plant 
life. Research thus far indicates that phenothiazine and a few other 
organic chemicals are promising; in this respect, 
CLEAR LAKE GNAT 
Nonbiting midges of the genus Chaoboms which breed in enormous 
numbers in certain bodies of fresh water are a source of great annoy- 
ance to nearby residents and visitors to resorts in a number of locali- 
ties in the United States. To determine methods of controlling them 
a field laboratory was established at Nice, Calif., on Clear Lake, 
where these insects are unusually abundant. Since relatively little is 
known of the biology of the gnats, considerable work has been neces- 
sary to determine their rather intricate life histories and their rela- 
tionship to environmental factors. Preliminary studies have been 
made also to determine the value of various biological, chemical, and 
mechanical methods of destroying the gnats, but thus far nothing 
practical has been developed. 
INSECT SECRETIONS 
Extended research into the physiology of insect secretions has 
developed the fact that blowfly larvae cause the production of am- 
monia in the material upon which they are feeding. This ammonia 
production appears closely associated with the healing effects of sur- 
gical maggots and with the attractiveness of screwworm-infested 
wounds in animals. Up to the time of these investigations no definite 
evidence had been presented showing how the larvae produced am- 
monia. It has now been discovered that the maggots secrete the 
enzyme urease, and this, acting on the urea present in the tissues of 
larvae as well as of the wound, causes the formation of ammonium 
carbonate and ammonium bicarbonate. These materials have been 
found to have a stimulating effect on the healing of obstinate lesions. 
TICKS AFFECTING MAN 
Investigations have been continued on methods of controlling the 
American dog tick, which transmits Rocky Mountain spotted fever in 
the East, A dip or wash composed of derris (containing 3 percent 
of rotenone), neutral soap, and water has been found effective in pre- 
venting complete engorgement of female ticks on dogs. If dogs are 
treated twice a week with this material, no reproduction of the ticks 
occurs. Tests are under w T ay to determine the feasibility of system- 
atically dipping all dogs in a given area for elimination of the ticks. 
Experiments are also being carried on to determine whether the de- 
struction of meadow mice, the principal hosts of the immature stages 
of the tick, will eradicate the ticks in limited areas. 
HOUSEHOLD AND STORED-PRODUCT INSECTS 
Investigation of a number of organic chemicals as possible moth- 
proofing agents shows encouraging results with one or two com- 
