BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 51 
A program was perfected for studies to determine the cause of outbreaks of 
those species of grasshoppers prevalent on croplands and to develop methods 
of preventing them. This study includes the annual survey for prediction 
of outbreaks of cropland species, and the establishment of permanent study 
areas to determine the cause and methods of prevention of outbreaks and to 
improve the methods of survey to make the prediction of outbreaks more 
accurate under the diverse conditions occurring in various States for the 
dozen or more species of grasshoppers of economic importance. 
Studies of baits have been continued. These are aimed at the development 
of a cheaper bait and one which would not compete with the feed market 
during periods of scarcity of livestock feed. These studies have indicated 
that molasses may be eliminated from the bait with little loss in effectiveness, 
and that sawdust covered with low-grade flour compares very favorably in 
effectiveness with the standard formula. Indications have also been obtained 
that the quantity of sodium arsenite can be reduced by one-half without 
materially affecting the killing power of the mixture. Further work with 
oil baits has indicated that certain species are not so readily killed by it as 
others. The demand still remains for a cheap, attractive bait that will remain 
effective for several weeks after distribution. 
Observations on the effect of the range species of grasshoppers have indi- 
cated that large areas of grazing land were completely denuded by grasshopper 
attack, and that in considerable portions of the Montana area grazing condi- 
tions would have been greatly improved in spite of the drought had grasshop- 
pers been absent. Studies are under way on the food habits and biology of 
the more important of the score or more species of grasshoppers that occur in 
abundance on range lands, and a study has been initiated to determine the 
possibility of preventing outbreaks on the range by controlling the grasshoppers 
in restricted areas during periods when their numbers are small. 
MORMON CRICKET 
Extensive outbreaks of the Mormon cricket occurred iu Montana, Idaho, Wyo- 
ming, Nevada, and Utah. Assistance was given to the States in organizing 
control campaigns, and these were conducted under emergency funds. A test 
was made of airplane dusting for control of the Mormon cricket. The results 
were satisfactory as far as distribution of the dust was concerned but the mor- 
talities obtained were low. The standard method of control by the use of 
hand dusters is more expensive than that in which baits are used and requires 
an excessive amount of labor. In the attempt to produce an attractive bait 
that will be effective in Mormon cricket control, a large number of materials 
have been tested without consistent results. 
INSECTS ATTACKING STORED CEREALS 
Investigations, by entomologists and chemists of the Bureau, of fumlgants 
and fumigation for the control of insect pests of stored cereals have continued. 
The type of mill construction has a marked effect upon the efficiency of the 
fumigants. Mills of concrete and steel were found capable of holding killing 
concentrations of gas for at least 18 hours, as compared with only a few 
hours in the case of more poorly constructed mills. 
Improvements have boon made in the method of fumigating mills by piping 
hydrogen cyanide to the individual milling units. This mot hod is giving a higher 
degree of control than could be obtained by tho old mot hods and at a lower price 
and it is already being used by a number of mills. It has boon tested with a 
methyl formate-carbon dioxide mixture in place of the liquid hydrocyanic acid. 
but it did not give satisfactory results in these cases, owing, apparently, to the 
slower action of this mixture. A study of the effect in mill fumigation of short 
exposures to hydrocyanic acid gas showed that the percentage of Insects killed 
by the short exposures was nearly as high as for the Longer exposures and Indi- 
cated the possibility of using shorter fumigation periods with effective results in 
times of emergency. 
Experiments to dot ermine the behavior of some <>t' the common grain fumigants 
in large storage bins and on the effect of methods of applying such fumigants 
demonstrated the dependence of dosage on commodity load, the need of intro- 
ducing the gas at several points, and the advantage of forced circulation. Chlo- 
ropicrin was found to give 100-percent kill of the adult rice weevil, one of the 
