MICHIGAN ACADEMY OF SCIENCE. 
203 
SUMMARY. 
1. The work reported in this paper has to do with the contact insecticides 
only. Those substances which destroy insects when ingested have not been 
considered. 
2. The insecticidal, gremicidal and toxic values (for higher animals) have 
little or no correlation. 
3. It is possible to determine the relative strength or value of insecticides 
by immersing test insects in definite strengths of the insecticide, and noting 
the time required to produce death. 
4. The common bedbug ( Cimex lectularius ) appears to be the most satis- 
factory test insect. 
5. As yet the mode of action, the way in which the contact insecticides 
cause the death of the insects, has not been determined. 
6. Apparently the fewer the number of spiracles, the smaller their size, 
and the better they are guarded by hairs or valves, the more resistant is 
the insect to the contact insecticides. 
7. Chemical standardization of this class of insecticides is with our present 
knowledge impossible. With two substances, having essentially the same 
chemical composition, the insecticidal values may vary enormously. Even 
the same substance, prepared with what are apparently unimportant chem- 
ical variations, gives widely different insecticidal values. 
Detroit Mich., U. S. A. 
LIST OF TABLES AND CHARTS. 
Table T. Toxicity. 
“ II. Germicidal values. 
III. Insecticidal “ 
IY. Summary of Tables I, II, III. 
V. Coefficients deduced from Table IV. 
Chart I. Graphically illustrating Table V. 
