EXPERIMENT STATION BULLETINS. 405 



DO THE CONTACT INSECTICIDES UNDER CONSIDERATION ACT UPON 



OXIDASES, CATALASES OR REDUCTASES IN THE LIVING 



TISSUES OF INSECTS TO CAUSE DEATH? 



The experiments just described showed that the contact insecticides 

 under consideration did interfere witli the activity of the oxidases, cata- 

 lases and reductases in the tissue extract of P. cornutus. In the con- 

 centrated form, such insecticides affected all three of the enzymes (if 

 they may be so called) but usually not in the same degree. It was clear 

 that carbon disulphide, for example, affected the oxidases and catalases 

 more strongly than it affected the reductases — while gasoline, on the 

 other hand, had its most deleterious influence upon the reductases. 



Trial showed that oxidases, catalases, and reductases existed in the 

 tissue-extract of many caterpillars, pupae and adult moths, as well as in 

 the adults and grubs of various beetles. Also, reference has already been 

 made to the work of Batelli and Stern* in relation to oxydones in insects. 

 These authors, in the same year (1013), again described tyrosine-oxidase, 

 polyphenol-oxidase, and oxydones in several forms of insects. Besides, 

 a few other scattered references in literature briefly (often covertly) re- 

 late the occurrence of oxidases in the blood or in extracts from various 

 lepidoptera, beetles and diptera. Loew has recorded the presence of 

 catalase in three dififerent beetles. In fact, the occurrence of oxidases, 

 catalases and reductases in extracts appears to be as general among 

 insects as among other forms of life. 



Further experiments showed that extracts from tomato-worms did 

 not give the test for oxidase with alcoholic guaiac but hydroquinone- 

 oxidase and tyrosin-oxidase were clearly present as well as reductases 

 and catalases. Moreover, the influence of gasoline and carbon disulphide 

 upon the activity of extracts from white grubs (both Lachnosterna and 

 Allorhina) and tomato worms was similar to that already recorded in 

 connection with extracts from specimens of adult P. cornutus. 



With these facts established, the question remained as to whether 

 oxidases, catalases and reductases in the living tissues of P. cornutus 

 became deleteriously affected by contact insecticides used in such 

 amounts and for such periods only as were necessary to kill. That 

 catalases and reductases, as found in the tissue extract of the insect, 

 really existed in the living tissues (and were not after-products of the 

 tissues in the extract) seemed reasonably certain. If hydrogen peroxide 

 were introduced directly into the tissues in any part of the body of a 

 living beetle, oxygen became liberated at once with great energy; and the 

 reducing power of living animal tissues, generally, for methylene blue 

 is well known. In technical bulletin 11 (this station), page 52 is refer- 

 ence to the fact that living beetles, in the absence of oxj'gen gas, reduced 

 large amounts of indigo carmine and methylene blue which had been 

 injected into the body tissues by means of a fine hypodermic needle. Even 

 in the open air, a small amount of methylene blue, injected into the tis- 

 sues of a beetle's body, became entirely reduced. When the reduced 

 (leuco-) methylene blue was collected for excretion by the cells of the 

 Malpighian tubules, however, it became oxidized to the blue color again 

 in those cells. Still, this reoxidation of the color-body did not neces- 



•Batelli and Stern (Blocbem. Zeits., 1913, 56, 59-77). Rev., J. of the Chem. Soc, Vol. 

 103-104, part i, p. 1272. 



59 



