JOURNAL 



OF 



ECONOMIC ENTOMOLOGY 



OFFICIAL ORGAN AMERICAN ASSOCIATION OF ECONOMIC ENTOMOLOGISTS 



Vol. 8 DECEMBER, 1915 No. 6 



THEORY OF TOXICITY 



By C. W. Wood WORTH 



The most important work to be done in Economic Entomology is 

 to lay a foundation of sound theories. The necessity of such work is 

 well shown in the progress of fumigation where, for instance, the orig- 

 inal publication ^ contained tables of dosage calculated on the assump- 

 tion that the dose should be determined in proportion to the volume, 

 and this erroneous theory still influences the thoughts of entomol- 

 ogists, though discarded from the first in actual practice. Again, when 

 a careful study of the actual doses used for different sizes was made,^ 

 showing that the area of the tent corresponded much more closely 

 than volume to the practice of fumigators, there was a universal 

 adoption of this basis of calculation upon the erroneous theory that 

 such a table correctly compensated for leakage. The only way a 

 correct compensation can be secured is to measure the amount of leak- 

 age, which is now a very simple matter,^ and then to use tables cal- 

 culated for the various degrees of leakage.^ 



Each step in this progress was accomplished by efforts directed to- 

 wards correcting the theory, and required the accumulation of a 

 very large volume of data, since there are so many unknown variables 

 that individual experiments are entirely unreliable. Many thousands 

 of determinations were made in the study of leakage referred to above, 

 and a series of 40,000 lots of scale insect eggs were used in obtaining 

 the data discussed below. This quantity was not great enough to 

 eliminate all the irregularities in curves shown in plate 28, but is 

 without doubt the largest volume of laboratory data ever secured 



^ Bulletin 71, California Agricultural Experiment Station. 

 2 Bulletin 152, California Agricultural Experiment Station. 

 2 Circular 75, California Agricultural Experiment Station. 



* Joum. Econ. Ent., Vol. iv, pp. 376-380. Bull. 220 and 257, California Agricul- 

 tural Experiment Station. 



