MICHIGAN ACADEMY OF SCIENCE. 
197 
A CONTRIBUTION TO OUR KNOWLEDGE OF INSECTICIDES. 
C. T. McClintock, E. M. Houghton, and H. C. Hamilton. 
Having occasion to compare the value of certain coal tar products with 
other recognized contact insecticides, search was made for literature on the 
subject, particularly as to how they act on insects and what conditions 
would make for greatest efficiency, without, however, finding anything con- 
clusive. 
Some of the older naturalists notably Reaumur and Swammerdam had 
experimented with individual insects to determine whether the stoppage of 
the spiracles was the cause of death, and whether the functions of all the 
spiracles were the same. The conclusion that they differ, and that death 
follows the clogging of the posterior spiracles but not of anterior ones has 
been declared erroneous by Kirby and Spence in their text book, “Intro- 
duction to Entomology.” Dr. La Hille, chief of the Bureau of Applied 
Zoology to the Minister of Agriculture of the Republic of Argentine, in his 
‘‘Contributions to the Study of the Ixodes,” claims to have proved by ex- 
periment that immersion of the posterior part of the Boophilus Annulatus 
in an efficient insecticide is all that is necessary; immersion of the head for 
an equal length of time in the same solution not having any effect. This 
insect, however, has onlj’ two spiracles which are located in the posterior 
part of the body. 
These writers are exceptional either in having made experiments or having 
recorded them where they would be available. Different living authorities 
on such subjects profess themselves to be ignorant of the method of action 
of insecticides or have unproved theories as to hoyr the various contact 
insecticides might be efficient and as to the proper condition of the oil which 
forms the base of many of the best insecticides. 
American writers on economic entomology have confined themselves to 
mass action of insecticides, apparently caring little as to the selective action 
of the material or the comparative values of similar preparations. Finding 
nothing in the literature which would indicate how an emulsified oil might 
act on the insect, what different effects one might expect from the use of oils 
of different chemical and physical properties, the time seems opportune for 
a somewhat extended statement of the results we have obtained from our 
experiments. 
How does the character of the emulsion effect its insecticidal value? Do 
the insecticidal and germicidal values of the preparations depend on the 
same constituents? Is there any relation between those two properties and 
the toxicity toward higher animals? And, most important of all, can a 
laboratory test be made to determine the relative values of different insect- 
icides with any degree of accuracy, in other words, can they be stan- 
dardized? 
Since chemical standardization presupposes knowledge of what constituents 
and what forms of combination are necessary to produce a valuable product, 
and since one or both of these points are more or less enveloped in uncer- 
tainty, the present stage of our knowledge precludes the use of chemical 
methods or at most, only in part. 
