42 ANM AL KKPOK I S OF I >I ".PA li l .M 1 :N T uF A( ; KK TLTUKK. I'.KiT 
penetrate to the .'{(l-foitt level Jiiul that this method of fumigation is not feasible 
under the eonditions ordinarily eneountered. 
The minimum lethal dos«' of hydrogen eyanide, ethylene oxide, chloropicrin. 
ethylene diehloride, and earh(»n disulphide for exposures of 1, 3. and 24 hours, at 
72° to 70° F., has been determined for the rice weevil, the tlour In'etle. and the 
Mediterranean flour moth, and for the eggs of the last two species. In the case 
of etliyh ne oxide, the eggs of both the Hour beetle and the flour moth are 
more susceptible to the fumigant with a 24-hour exxK)sure than are their re- 
spective adults. With 1- an(l 3-hour exixisures the eggs of the tlour beetle 
are many times more susceptible to the gas than are the adults: the eggs of 
the Hour moth are e<iually suscei)tible with the adults for a 1-hour exiM»sure 
but only slightly more resistant for a 3-hour exi)osure. Hy«lroeyanic acid 
gas is more toxic to the egg of rhe Hour beetle than to the adult at all ex- 
posures, whereas the reverse is true regarding the egg and adult of the Hour 
moth. Chloropicrin, carbon diehloride, and ethylene diehloride are in general 
le.ss toxic to the eggs of the Hour beetle and Hour moth than to the adults, at all 
exposures. These results indicate the wide variatiitn in susceptibility to fumi- 
g-ants, not only of different sjx'cies of insects but of the dilYerent stages in their 
life cycle. 
Determination was made of the size and kinds of flour Ixdting cloth neces- 
sary to remove the eggs of the principal insects occ\irring in linished Hour. This 
information has already been adopted by the trade, and small unit sifters for 
redressing Hour and removing the insects have been developed. 
GRASSHOPPERS 
The annual grasshopper survey conducted in the fall of 1930 in cooperation 
with the States indicated that or.e of the most widespread grasshopi>er infesta- 
tions ever known was in prospect and that $-!.OvKi,lO() for the purcha.se and 
transportation of materials would be required to control the infestation. De- 
velopments during the spring and early summer of l:i37 fully justified this esti- 
mate and indicated that the survey had erred on the side of con.servaiism. par- 
ticularly in South Dakota and Colorado, where even more severe infestations 
developed than had been estimated. There was no detailed survey of Texas and 
New Mexico, where .severe infestations also developed. 
Congress made $1,000,000 available for grasshopper control late in April. 
States set up the organization required for cooperation, and .shipping of mate- 
rials for grasshopper bait was begun in May. V>y the end of June funds avail- 
able under this appropriation were practically exhauste<l although bait re^piire- 
ments for the infested areas were far from met. and it was necessary to retluce 
allotments to States to about half of the estimated requirement. Two factors, 
however, tended to ameliorate the shortage of Federal bait incurred by the limi- 
tation in fluids and the unprecedented shortage and high i)rice of bran. The 
fir.st of these was the adoption of a new formula for bait, developed by research 
during the previous year, which made it possible to increase the sawdust in 
the mixture from the nO percent previously used to 75 percent through the u.se 
of bran containing the shorts and middlings. The second was the much greater 
contribution of materials by States, counties, and individual farmers than in 
any i)revious Federal camjiaign. Some States furnished all the materials re- 
(pnred except the poison, and many of them supplied all of the sawdust need(Ml 
in the mixture. 
The development of an extensive outlireak of the loni;-winged miirratory grass- 
hopp<'r in eastern Colorado and northwestern New Mexico created an emer- 
gency which prompted the governors of those States to call out the National 
Guard. In these sparsely s(>ttled areas farmers were unable to supply tlie labor 
for mixing stations and distribution of bait and the transportation of materials 
needed to prevent complete lo.ss of crf>ps and a subsequent migration of this 
truly migratory sjiecies into more productive areas of these and adjoining 
States. 
Hy the end of tlie liscal year b.iit niaterials li.-id been shipped into Arizona. 
Arkaiis.-is. California. Colorado. Illinois. low.i. Kansas. Michigan. Minne.«*ota. 
Missouri. Montana. Nebraska. New Mexic(», North Dakota. Oklahoma, South 
Dakota, Tcx.ms. I'tah. Wi.sconsin. and Wyoming. 
Thr full results of this cjunpaign cannot be determined until the end of the 
siunmer. when an estimate of lo.s.^(>s and savings will be av.Milable. (iiMierally 
succe.s.»iful results have been reported wlu're it has been |>o.s.sible to supi)ly suffi- 
cient baits and where good crop prospects have encouraginl the farmers to con- 
sistent control cfTort. 
