EXPERIMENT STATION BULLETINS. M'.) 



of various liquids and vapors upon the heart action of Passalus cornutus 

 could be readily studied. A beetle, elytra and wings removed, could 

 be so placed in the cell that the dorsal surface of the abdomen touched 

 the face of the upper thick glass cover. In that position, upon the 

 stand of a binocular microscope, the rate and peculiarities of the 

 heartbeat in air alone, could be carefully observed for some time. 

 Then, when the liquid, vapor, ior gas was passed into the cell through 

 its tube connections, the influence upon the heart could be followed 

 from the very start. 



The insecticide vapors and gases used in connection with the study 

 of effects upon movements and the general behavior are as follows: 

 gasoline, kerosene, benzol, xylene, turpentine, creosote, aniline oil, 

 carbon disulphide, chloroform, ether, pyro cresol, special kreso-dip, 

 creolin, chloro-naphtholium, crel oil, zenolium, to-bak-ine, pyrethrum, 

 hydrocyanic acid gas, carbon dioxide, nitrogen and hydrogen. The first 

 five of these, also pyrethrum, carbon dioxide and hydrogen were used 

 in studying the effects uipon heart activity. 



It is not of advantage, here, to relate separate experiments with 

 each of these substances. Results varied considerably with different 

 substances used on the same species as well as with the same substance 

 upon different species and individuals. But certain general facts 

 seemed of importance in this study. — If insects were treated with any 

 of these substances in exceedingly small am^ounts at first, and the 

 amounts were afterward gradually increased, a period of excitement 

 was usuall}^ very noticeable. In some instances this was mild and in 

 others, the insect rushed about in a perfect frenzy. This period was 

 followed by one of uncertain, or uncontrolled movements and finally 

 by the entire loss of movement and sensibility. The latter stage was 

 followed more or less rapidly by death. In the* second stage with un- 

 controlled movements the insects were often sick and would spew 

 secretions from the mouth. This was almost invariably the case with 

 CeiUhophilus in gasoline vapor. The length of time that any one of 

 these stages would last varied widely with the substance, the amount 

 of it used, and with the insect. The heart action during the period of 

 excitement became greatly quickened and irregular. Sometimes the 

 pulsations followed one another along the dorsal vessel with such 

 rapidity they could not be qounted. Then the action would stop en- 

 tirely for a ilittle while. When the excitement period of the insect had 

 passed, the heart action was still apt to be irregular but the beating 

 always became slower and gradually fell far below the normal. As a 

 rule, however, the heart action was one of the last visible signs of life 

 to disappear. The time limit, for which insects could endure the period 

 of absolute loss of motion and heart action, varied as much or more 

 than any other one thing. In case of some insecticides there might be 

 no recovery at all of certain species, if this stage were reached. In 

 fact, Ceutliophilus was almost certain to die without complete recovery, 

 if even the second stage were reached and the insect became sick from 

 gasoline vapor. Insects plunged into large amounts of the vapor or 

 gas of any of the very volatile fluids passed a quick excitement stage, 

 followed almost instantly by absolute loss of motion. Carbon-dioxide, 

 nitrogen, and hydrogen produced quick insensibility, too, as a rule; 

 but if these gases were admitted gradually, the general symptoms al- 



