548 STATE BOARD OF AGRICULTURE. 



came very apparent: first, tissues of caterpillars were not vlsably affect- 

 ed by kerosene and gasoline nntil several hours after death had resulted : 

 second, an alkaline wash might penetrate the chitin, gradually dis- 

 solving the fat body and muscles in the treated portion of the liody 

 while the rest of the body was alive. In the latter case, it seemed rea- 

 sonable to attribute final death to this solvent action. Likewise, when 

 corrosive sublimate was used on bed-bugs, or other delicate-bodied in 

 sects, it slowly penetrated the chitin and precipitated the proteids 

 of the tissues, so that death might reasonably be attributed to that 

 action. There was apparently, no measurable period of time between 

 the condition showing the usual attributes of death in a tissue and the 

 occurrence of the precipitation mentioned. This was true in case of 

 all the solutions usually spoken of in histological methods as "fixing or 

 killing agents/' Alcoholic solutions of these agents (where such can be 

 made) penetrate chitin more rapidly than water solutions. Heat, 

 which causes coagulation of the proteids is also such an agent. It 

 penetrates chitin more quickly than any other fixing agent. 



EFFECT OF CONTACT INSECTICIDES AFTER ABSORPTION. 



Proof that some of the liquid contact insecticides become absorbed 

 by insects was seen in the readil}^ visible effects upon the body tissues. 

 For that reason, the effects of these liquids have already been mentioned 

 under the last heading. It was noted there that kerosene, gasoline, 

 and indeed a large part of the list of fluids whose vapors were found to 

 affect insects, made no visible change in the tissues for several hours 

 after they were applied externally in abundance. In fact, death re- 

 sulted before the liquids, as such, had penetrated the body, and physi- 

 ological disturbances began at almost the moment insects were treated 

 with these liquids or their vapors. It appeared, then, that the volatile 

 portions of the fluids penetrated into the tissues rapidly. Attention 

 was therefore given to a study of some of the important physiological 

 effects of the fluids in question. The work done on this phase of the 

 subject might be classified under two general headings: (a) effects 

 upon the general activity and heart-action and (b) effects upon respira- 

 tion. 



(a) EFFECTS UPON THE GENERAL ACTIVITY AND HEART ACTION. 



In order to study the influence of vapors upon the general activity 

 and behavior of insects, they were confined in the air of broad shallow 

 vessels, upon screens, above the fluids to be used. A vessel containing 

 its fluid, was left standing for some time until the air confined was 

 saturated with the vapor at the temperature of the experiment. The 

 insect was then introduced upon the screen and (Observations taken. 

 Passalus cornutus and Geuthophilus sp. were the insects piincipally 

 used, but plant lice, Diptera, a few Hymenoptera and others were also 

 tried during the course of the experiments. For making a study of 

 insect activities in such gases as carbon-dioxide, hydrogen, or nitrogen, 

 the confinement was made in glass containers above mercury. One 

 other method for studying the behavior of Passalus cornutus in hydro- 

 gen has already been described and the apparatus figured; see Fig. 1. 

 It was by means of the cell "J" represented in this figure that the effect 



