Two-spotted lady 

 beetle 



Following the period of growth there comes a time of 

 apparent rest and change which, with the butterfly, is 

 known as the chrysalis, and finally we have the insect 

 or butterfly itself. A knowledge of 

 these changes is interesting and also 

 valuable, since there is almost always 

 some period in the growth of an insect 

 when its habits make it rather easy 

 to control. Leaf-feeding caterpillars 

 and grubs may usually be killed by 

 spraying with a poison (such as arsen- 

 ate of lead which is one of the best 

 poisons), while this would be of no 

 value for such a pest as bark or twig borers, because 

 the poison can not be placed where the insects must eat 

 it or go hungry. Plant lice, since they suck the fresh 

 sap from the inside of the leaves or the inner or under 

 part of the hark, can not be killed by poisons lying on 

 the surface; fortunately they are very delicate and most 

 of them are easily killed by spraying the insects them- 

 selves with a mixture of soap and water. Scale in- 

 sects, like plant lice, suck the sap from the plant but 

 they are more difficult to kill because they are protec- 

 ted by a waxy scale. We must either use a stronger 

 spray and apply it in winter so as to avoid injuring the 

 plant, or else wait for the time when the tender young 

 are crawling and kill them with a 

 spray such as is used for plant lice. 

 Borers can be destroyed only by 

 putting something into the burrows 

 which will kill the grubs, such as car- 

 bon bisulfid, or by cutting and burn- 

 ing the infested parts of the tree. 



The habits of insects difter so 

 much that we must know what each 

 pest actually does before we can 

 fight it to the best advantage. The 

 elm leaf beetle and the white-marked 

 tussock moth are both leaf feeders, 

 and yet a tree may be sprayed in 

 such a manner as to kill the cat- 

 erpillars of the latter and not injure the elm leaf 

 beetle grubs because they feed entirely on the under 

 surface of the leaf and are therefore not afl'ected by a 

 27 



wingL-d fly 



