REPORT OF THE ENTOMOLOGIST. 



329 



only by contact, and its action on many larvae is marvelous, the small- 

 est quantity in time paralyzing and ultimately killing. Its influence 

 in the open air is evanescent, in which respect it is far inferior to the 

 arsenical products; but being perfectly harmless to plants it can fre- 

 quently be used on vegetables where the more poisonous substances 

 would be dangerous. Pyrethrum is supposed to have no effect on the 

 higher animals, but that is a mistake, as my own recent experience is 

 that the fumes in a closed room have a toxic influence, intensifying sleep 

 and inducing stupor; while the experience of Prof. A. Graham Bell, 

 with the powder copiously rubbed on a dog, showed that the animal 

 was made sick and was affected in the locomotive organs very much as 

 insects are. The wonderful influence of this powder on insects has led 

 me to believe that it might prove useful as a disinfectant against fevers 

 and various contagious diseases by destroying the microzoa and other 

 micro organisms, or germs which are believed to produce such diseases. 

 It should be tried for that purpose. It is remarkable that these two 

 plants of all the many known species of the genus should alone possess 

 the insecticide property. 



Of all insecticides to be used against root-feeding or hypogean in- 

 sects, naphthaline, sulpho-carbonate of potassium, and bisulphide of 

 carbon are the chief. Dr. Ernst Fischer, in a recent work, has shown 

 that naphthaline in crystal may be satisfactorily used under ground, 

 destroying by slow evaporation. But bisulphide of carbon still holds 

 the hist place in France against Phyllo.rera vastatrir. It is conveyed 

 beneath the ground at the rate of one-half to one kilogram per vine by 

 special injectors, or by more complicated machinery, drawn by horses. 

 I believe that petroleum emulsions will supersede it as an underground 

 insecticide, and prove to be the best we have, cheapness, safety, and 

 efficiency considered. This glance at the chief insecticides now in use 

 may convey some idea of the recent progress in this direction, but will 

 convey no idea of the far greater number of substances, whether drawn 

 from the animal, vegetal, or mineral kingdom, that have been experi- 

 mented with and found wanting. After the 1 discovery of a satisfactory 

 insecticide, however, various important problems must be solved, and, 

 particularly, how to apply it to greatest advantage, having safety to 

 man and stock, harmlessness to plant, and economy, in mind. The so- 

 lution of these points, and others that the peculiar habits of the insect 

 to be controlled involve, brings us to the question of mechanical con- 

 trivances ;nid appliances: for while much ingenuity has been exhibited 

 in devising mechanical menus of directly destroying noxious insects 

 without insecticides, it is chiefly in the proper application of these last 

 that the greatest mechanical advances have been made both in this 

 country and in Europe. 



Here, again, the subject is so vast that T cannot enter into details. 

 One can form some idea of the recent activity in this direction by glanc- 

 ing at the figures in the First Report of the United States Entomologi- 

 cal Commission on the Rocky Mountain Locust, my bulletin on the Cot- 

 ton-worm, and other official publications. Perfection here, as in other 

 kinds of mechanical appliances that aid man's progress in art and sci- 

 ence, is usually the slow outgrowth of tedious trials. However brilliant 

 the original theoretical conception, the practical details are almost al- 

 ways the result of sheer experiment and trial. Failures precede suc- 

 cess. Yet success will usually follow in proportion as certain principles 

 are kept in mind covering particular needs in special cases — principles 

 deduced from entomological studies. 



