INTRODUCTION. 5 



of many. The grasshoppers, crickets, and cockroaches, and the 

 sucking bugs, including the Chinch-bug and Squash-bug and the 

 plant-lice, do not have a quiescent pupal stage. The young, when 

 hatched from the egg, resemble the parent form, having the same 



Fig. 6. Rocky Mountain Locust, an insect which undergoes " incomplete meta- 

 morphosis; " a, b, c, young forms; d, adult. 



kind of mouth-parts, but lacking wings. The wings soon begin 

 to appear as small pads, which grow larger as the insect increases 

 in size. The insect moults or casts its skin several times before 

 reaching maturity, and at each moulting the wing-pads are seen 

 to be considerably larger than before. The young of these insects 

 sometimes differ in color from the adults, e. g., young Chinch-bugs 

 are red, the adults blackish. These insects are said to undergo 

 an incomplete metamorphosis, the immature forms being active 

 all the time, feeding all the time, and, what is important to us, 

 injurious all the time. We are talking now, of course, of injuri- 

 ous species. 



It is necessary, then, to know something of the structural char- 

 acters and the life-history of each insect pest with which we wish 

 to cope. Where and when are the eggs laid? What are the 

 characters and habits of the young? What is the duration of 

 the larval stage? Where and when does pupation take place? 

 duration of pupal state? time of appearance and egg-laying of 

 adults? in what life-stage does the insect hibernate? These and 

 many other questions are to be answered before the economic en- 

 tomologist can see his way to the most feasible method of fighting 

 the insect pest under consideration. 



