APriJCATIONS TO 1»KK\KNT OV Il^oSITIoN. 143 
The pyrothruin and water mixture is ])rej)are(l \)\ stiriinir np as 
miieh of th(* powder as IIk^ wat(M- will hold in susjxMision, or n little 
milk may 1)(> adihul lo incri^ase \\\o lioldinii; J)o\\(M* of the watci". Tlic 
residts obtained with j)yrethrnm in \\at(M- against the transformed 
insects are as satisfactory as with the di-y ])()\\(lcr, with the additional 
advantaixe of its hcini:; j)ossil)lc to throw \\\c watci' hy forces pumps to 
])arts of the |)lant whiu'e it would \h' dillicult to i)lace the powder. 
Airainst the j)uj)a\ the water solution is more ell'ective than the 
])ow(l(M', hut is l(^ss so than kcM'oseiu* emulsion. 
Kerosene (unulsion, as an a])i>lication for d(\strovintjj the emer<r(»(l 
])U])a^ and adults, is us(m1 in V(M-v stron^i: solution, or at a strength 
ranixinii: fi'om oni^ j)art of the emulsion to one of wat(M" uj) to a dilution 
of the enudsion with ei*^ht ])arts of water. The <j^reat(M' stren<^ths were 
more innnediate in their effects, but even with the more (lilut(Ml washes 
very satisfactory results have been obtamed. The enudsion at once 
stops all molting or transformation. Applied to the partly trans- 
formed insects, the soft wings harden into shapeless masses, and while 
occasional individuals may survive the treatment for two days or 
more, the a])])lication is usually fatal in the end. The treated pup« 
are iniable to transform to the adult stage and they eventually die or 
are devoured by their natural enemies. The death of the mature and 
hardened insect is caused by closing its breathing pores A\dth the oily 
mixture, and in the case of the partly expanded or soft, immature 
individuals by the caustic effect it has on the forming wings and soft 
body. 
The experiments with acids demonstrated also that exuviation may 
be prevented by spraying the newly emerged pupa with a 2 per cent 
solution of carbolic acid or a 15 per cent solution of acetic acid. 
Applications to Prevent Oviposition. 
All the early experiments with washes or other applications to 
prevent oviposition proved unavailing except such protections as 
could be a])plied to small trees or shrubs, such as covering them wdth 
netting. Professor Riley in 1868, and later, at his instance, Dr. 
W. S. Barnard, tested a number of repellent substances, such as 
kerosene emulsion, various oils, and carbolic-acid solutions, all ]nin- 
gent and disagreeably smelling sid^stances, with results either unsat- 
isfactory or of negative value. 
In the occurrence in 1902 of Brood X souk* indications were obtained 
showing the possible protective value of lime washes. Mr. Slinger- 
land reports that spraying a heavy coat of whitewash on the trees 
will keep the locusts away to some extent when there are other 
tre(vs in the neighborhood, lie states that the reason for this seems 
to be that the insects do not like to sit on a white surface. The 
