FIELD WORK ON INSECTS. 51 



secrets through its round disk. A hand lens magnifying 

 about fifty diameters is highly useful for the smaller 

 insects. 



Another requisite, which is used for disposing of 

 noxious insects, and such others as may really be needed 

 for examination, is a killing bottle, or other means of 

 killing your 'insects. Beneficial insects should not be 

 killed ; but all noxious insects should be killed. To avoid 

 making any mistakes, all insects should be taken alive 

 and studied in that condition; then the advice of the 

 instructor is to be followed as to whether to kill your 

 ' ' find " or not. Every living creature has its mission, and 

 the day has gone by when we can afford to destroy bene- 

 ficial animals of any kind; and you will attain one of the 

 most valuable results in field zoology if you learn which 

 are our familiar, beneficial insects and which are the 

 harmful ones. 



Having the knowledge that some of your insects 

 will deserve killing, it will be necessary to have a small 

 bottle of gasoline for use in killing the grasshoppers, the 

 katydids, and the locusts. These are big coarse insects, 

 are not beneficial, and their bodies are not delicate enough 

 to be harmed by the action of the gasoline. The fumes of 

 the killing bottle do not readily affect them; they suffer 

 long, and sometimes come to life on the pin after you are 

 reasonably sure that they are dead ; and there is never any 

 excuse for causing needless suffering. The animal with 

 a highly organized nervous system dies quickly ; we often 

 hear of "instantaneous death" with respect to such 

 animals. But animals of less complexity are not so 

 quickly affected, hence die more slowly. The grasshop- 

 pers all die more slowly than do the flies, the bees, or the 

 butterflies. 



