- 22 - 
of this the results of tests with one species are about the same as those 
with another. Severin (i&Ji) reported chlordane to he effective against 
35 species of grasshoppers. 
fielative toxicities of chlordane and other insecticides to frass- 
hp-p-pers - In the laboratory Koarns e_t &1.. ( 2^5 ) made stomach poison testa 
with chlordane, DDT, and gamma-BHC on the adult grasshopper Melanoplus 
differentialis (Thos.). Emulsions of xylene solutions of the active com- 
pounds were fed to the grasshoppers in measured drops. Twanty-four hour 
mortality records indicated the median lethal dosage for gamma-BHC to lie 
between 5 ^ad 10 micrograms, for chlordane between 12.5 and 25 micrograms, 
and for DDT to be greater than 50 micrograms per gram of body weight. 
Ehoades and Brett ( 3&3) made laboratory tests on three economic 
species of grasshoppers, Melanoiolus bivittatus (Say), M. djff erentlalis 
(Thos.), and M. mexicanus mexicanus (Sauss.), to deterrr.ine their suscepti- 
bility to certain synthetic insecticide dusts under different constant 
temperatures. A 10-percent chlordane dust was slower acting than 2— per- 
cent parathion and 5-parcent gamma-BHC dusts, requiring from 43 to 72 
hours to reach peak mortality. High temperature increased its effective- 
ness to a lesser extent. Chlordane was less effective than the other 
materials except DDT in its action as a contact toxin. There was little 
difference in the relative susceptibility of the three kinds of grass- 
hoppers to the different insecticides. 
In laboratory tests against Zpnocerus elegans (Thunb.) by Petty 
( 363 ) in South Africa a 2-percent parathion dust proved superior to a 
5-percent chlordane dust. In general, 10-percent BHC causes a quicker 
rate of mortality than 5-percent chlordane, although the final mortality 
obtained with the two insecticides is similar. A 5-percent BHC con- 
centration appears to be too weak for effective control and 10-percent 
DDT is relatively ineffective. There is some indication that young 
hoppers are more susceptible to the poisons than the older ones or 
adult insects. The results suggest that a 5-percent chlordane dust 
should be effective at the rate of 20 pounds per acre. 
LePage e_t ai.. ( 297 ) in Brazil, using Schistocerca caacqllata. (Serv.) 
as the test insect, found that a 5-percent chlordane dust was more toxic 
than dusts containing 10 percent of dinitro compounds or 20 percent of 
toxaphene but was less toxic than dusts containing 0.25 percent para- 
thion, or 1 percent of gamma-BHC. 
Kearns e_t ai.. ( 246 ) made laboratory tests on the grasshopper (}{, 
differential^ ) . housefly, American and German roaches, milkweed bug, 
codling moth larvae, black carpet beetle, webbing clothes moth, plum 
curculio, chinch bug, and two-spotted mite with several insecticides. 
The relative toxicity of these materials was: dieldrin^> aldrin = hepta- 
chlor ■ gamma benzene hexachloride > chlordane > toxaphene > DDT. The 
residual effectiveness of the materials was: dielirin> DDT >aldrin.> 
heptachlor = chlordane.^ gamma benzene hexachloride. 
