580 Journal of A gricultural Research voi. xii, no. 9 



and acetone are as toxic as gasoline. Von Prowazek (8) recommends 

 xylol and ether for the destruction of lice and their eggs. 



In view of the work of the senior author (5, 6) showing that the toxicity 

 of organic compounds to insects is related to their volatility, of which 

 the boiling point is a general index, it was thought advisable to make 

 a similar study of the toxicity of a series of volatile organic compounds 



to insect eggs. 



METHOD OF EXPERIMENTATION 



For these experiments it was considered desirable to use eggs which 

 were not protected from the action of the chemical by any covering. 

 Eggs of the bedbug and the clothes louse were considered; but, owing 

 to the fact that many of these eggs were found to be infertile under 

 the artificial conditions of breeding, and, further, that they were hard 

 to obtain in large enough quantities for the purpose of the experiments, 

 they were discarded. Potato-beetle eggs (Leptinotarsa decemlineata 

 Say) were finally decided upon as fulfilling all requirements. As many 

 as 50,000 eggs were used in these experiments, and it was found that 

 in every case untreated eggs hatched 100 per cent. They were also 

 convenient to use, as a cluster of 20 to 30 or more eggs could be easily 

 treated as a unit. The effects of the chemicals were studied in three 

 different ways: 



1. By dipping the clusters in the chemical to be tested. 



2. By spraying the clusters with the chemical by means of an atomizer. 



3. By exposing the eggs to the action of the vapor of the chemical. 

 In the exposure to the vapor the eggs were fumigated in a similar 



manner to that employed in the study of the toxicity of the vapor to 

 houseflies recorded in a previous paper (6). It was found necessary, 

 however, to use a longer time limit than 400 minutes, 15 hours being 

 finally selected for this purpose. 



Eggs were fumigated for 15 hours with varying quantities of the 

 chemical, after which they were removed from the flask and placed in 

 open pasteboard pill boxes until they hatched or were undoubtedly 

 dead. The smallest dose necessary to kill the eggs in this length of 

 time was thus determined and reduced to millionths of a gram-molecule, 

 making possible an accurate comparison of the different chemicals used. 

 In experiments where the eggs were dipped or sprayed they were placed 

 in open pill boxes after treatment and handled in a manner similar to 

 those fumigated. 



RESULTS OF THE EXPERIMENTS 



The results of dipping and spraying the eggs are given in Table I. 

 The compounds used are arranged in the order of their boiling points, 

 from the lowest to the highest. It will be noted that in general the 

 eggs treated with compounds having the lowest boiling point — that is, 

 the most volatile compounds, permitted most, if not all, of the eggs to 

 hatch. Exceptions may be noted of compounds extremely active 



