252 EXPERIMENT STATION RECORD. 



parasites of insects are brought togetlier, and additional data by R. R. Parlier 

 follows (pp. 246, 247). 



Notes on the onion magg-ot in 1914, A. I. Boubne (Jour. Econ. Ent., 8 {.1915), 

 No. 2, pp. 276-279). — A report of work carried on in continuation of that pre- 

 viously noted (E. S. R., 31, p. 350). 



How contact insecticides kill, G. D. Shafer {Michirjan Sta. Tech. Bui. 21 

 (1915), pp. 67, pi. 1, figs. 3). — In this second report, which forms part 3 of the 

 studies previously noted (E. S. R., 26, p. 753), the author considers certain prop- 

 erties of carbon bisulphid, gasoline, and a few other fluids, as well as tempera- 

 ture and some dry powdered contact insecticides by means of which the insecti- 

 cidal action of these agents is accomplished after their absorption into the insect 

 tissues or after mere application. 



The general conclusions drawn are as follows : 



" Reductases, catalases, and oxidases were found in water extracts and in the 

 insoluble pulp of the tissues of Passalus cornutus and other insects. ^loreover, 

 almost certain evidence indicated that the same three kinds of enzyra-like bodies 

 exist in the intact tissues of living insects. Heat of certain intensities, and the 

 several contact insecticides studied (gasoline, carbon disulphid, hydrocyanic acid 

 gas, sodium fluorid, etc.), when used at a concentration sufficient to kill insects, 

 deleteriously affected the activities of reductases, catalases, and oxidases — 

 usually in unequal degree, thus disturbing the natural or normal balance of such 

 activities. If the catalase, oxidase, and reductase activities are actually of as 

 vital importance to the life processes of the tissue cells as certain evidence indi- 

 cated, then the deleterious action of the contact insecticides studied in this con- 

 nection must be an important factor — perhaps, in some cases, the determining 

 factor — in causing the death of treated insects. 



" A study of the influence of the various contact insecticide.? upon the life 

 processes in nervous tissue cells seems of next importance In this connection. 

 Fat or fat-like membranes (e. g., lard and lanolin) absorbed ga.soline vapor (and 

 chloroform vapor) from air charged with that vapor, and the absorbed vapor 

 rendered the membranes less permeable to oxj-gen. This finding may, in part, 

 account for the fact that less oxygen was used by an insect deeply under the 

 influence of gasoline, since a similar condition existed — in that, under such cir- 

 cumstances, the lipoids of the living, oxygen-absorbing cells, and of the body 

 fluids surrounding them, were impregnated with gasoline. So also, the same find- 

 ing may help to explain the fact tliat. in the presence of air containing gasoline 

 vapor, less hydroquinon was oxidized in an ' insect tissue extract plus hydro- 

 quinon solution' (in which the reductase had mostly passed) than was the case 

 when the same extract was in pure air. 



" "Waxen membranes which had been thoroughly wet with lime-.sulphur solu- 

 tion were found to be less permeable to oxygen than before they were treated 

 with the solution. Thus lime-sulphur, in addition to its effect as described in a 

 former paper, would render the waxen covering of a scale insect less permeable 

 to oxygen. 



"Pupre of the luna moth and adults of P. corntitus in a dormant condition 

 from cold absorbed much less gasoline vapor or vapor of ether in air than did 

 the same insects when they were most active, at a warm room temperature, in 

 air charged with practically the same percentage of vapor. This lowered 

 absorption capacity which was found to accompany the dormant condition may 

 furnish the chief explanation of the fact that insects dormant from cold are 

 harder to kill by ordinary fumigants and by those contact sprays which depend 

 partly upon volatile insecticide ingredients for their effectiveness. 



" It was found that certain nonvolatile, powdered solids were able to net as 

 effective contact insecticides when used on certain insects. Such dry, powdered 



