Insect^ Injarioas to ^Vapk Trees. 



BY E. P. FELT, D. Sc., STATE ENTOMOLOGIST, 



UNIVERSITY OF THE STATE OF NEW YORK. 



THE conditions under which shade trees are grown vary so widely from those 

 under which the same trees live in the forest, that methods of controlling 

 injurious insects found practicable in the one case can not be advised in the 

 other. For this reason the present paper will be confined to insects affecting shade 

 trees, and space limitations render it advisable to treat of only a few of the most 

 injurious species affecting maples. It will be found, however, that most of these 

 pests attack other shade trees, and that in one instance at least, that of the white 

 marked tussock moth, the caterpillars prefer the horsechestnut ; but as maples 

 are the more abundant shade trees throughout the state, even this species is of 

 greater importance on account of its injuring maples than because it attacks the 

 horsechestnut. 



Transformations. Before treating of individual species, it may be profitable to 

 glance briefly at the life history of insects and the relation of the various stages to 

 each other. All insects hatch from eggs, which present widely variable forms in 

 different species and are frequently of exceedingly beautiful design. In certain cases 

 the ova or eggs hatch within the body of the parent. Members of the very lowest or 

 simplest order of insects, such as snow fleas, slides or silver fish and their allies, 

 undergo no transformation, that is, there is very little difference between the young 

 and the adults. Among grasshoppers and related insects, there is what is called an 

 incomplete metamorphosis or transformation. The young grasshopper, as it emerges 

 from the egg, is a curious, wingless little creature, bearing a general resemblance to 

 the parent and can easily be recognized as a grasshopper. As the little fellow 

 increases in size, it casts its skin from time to time and with each molt the wing pads 

 become longer and in the final change the wing cases are slipped off and the organs 

 of flight are at liberty to perform their proper functions. In the stage before the final 

 one, the wing pads may be as long as the fully developed wings, but the two stages 

 may easily be separated by the position of these organs. In the adult the fore wings 

 fold over and conceal the hind ones, while in the immature grasshopper the hind wing 

 pads are outside of the fore ones. Many insects like cockroaches, walking sticks, 

 dragon flies, true bugs and others develop in this manner, but not all resemble the 

 adult so closely in the earlier stages as do grasshoppers. 



