162 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 2 



grees the dosage usually recommended will produce but about 1.2 per 

 cent of a saturated atmosphere, while at 50 degrees it will produce 

 about 2 per cent of a saturated atmosphere. 



Another consideration involved in interpreting the results as given 

 by various writers for the treatment of insects is the possible tem- 

 porary asphyxiating effect of the gas, Avhieh does not produce ultimate 

 death. In all of the records where we have found mention of the time 

 of making examination to determine the effect of the treatment, it 

 seems that the examination has been made immediately at the close of 

 the treatment. In the absence of statements to the contrary, it seems 

 reasonable to assume that this was probably the case in nearly, if not 

 quite all, of the experiments. Our own observations have led us to be- 

 lieve that such immediate examinations are very liable to lead to incor- 

 rect conclusions. We have made it a practice to preserve the appar- 

 ently dead specimens in each lot as well as the living for continued ob- 

 servation following the experiment. The first effect of the gas is to 

 stupify the insects and this occurs some time before actual death takes 

 place. Thus it is quite possible that in a case where all of the in- 

 sects appear to be dead on an iimnediate examination, a large percent- 

 age of them will recover upon exposure to the air or under the gradual 

 dissipation of the gas. It may require from one to two days for them 

 to resume normal activities. Some of those which thus become active 

 may indeed be so seriously affected that they cannot recover the ability 

 to feed and so ultimately die as a direct result of the treatment. The 

 standard which we have therefore adopted for our own work is to 

 count as "living" only those insects which subsequently resume their 

 normal activities, either in feeding and in reproduction, or in develop- 

 ment and transformation. If they do not thus recover it is evident 

 that the treatment is ultimately and practically effective. 



It is not our purpose in this paper to review the work of other en- 

 tomologists with Carbon di-sulfid, or to question specifically the report 

 of any experimental results. Nor shall Ave attempt to compare the rec- 

 ords of our own experiments with those of any other workers. We 

 have called attention to the apparently foreign origin of our most com- 

 monly accepted recommendations for its use and to a few of the many 

 chemical, physical and entomological considerations which seem to have 

 an important bearing upon the interpretation of prcA-iously accepted 

 results, merely to show that from our point of view the entire subject 

 of the use of Carbon di-sulfid as an entomological fumigant is still an 

 open question, so far as the scientific points involved in its use are con- 

 cerned, and that this therefore constitutes an important field, deserving 

 the most careful and thorough investigation possible. 



