FOREST ENTOMOLOGY. 



In many cases where we have incomplete metamorphosis, the insect 

 is injurious in all its respective stages, as, for instance, in Aphidse 

 and Cicadse. On the other hand, when the metamorphosis is com- 

 plete, we find the insect injurious in larval and perfect stages, or 



Fully developed Tortolscshell Butterfly. (Flatters & Garnett.) 



simply injurious in the larval stage alone. The perfect insect (or 

 "imago," as it is termed in entomology) often takes no food what- 

 ever, except sipping water or juices, and the duration of life is often 

 so short as to have become proverbial. 



As a branch of economic entomology, the student of forest insects 

 should strive to ascertain where and when egg-deposition takes place, 



how long the insect remains in 

 the egg stage, how long before 

 the first moult and between the 

 other larval moults, when and 

 how long it remains in the pupal 

 stage, and the time and appear- 

 ance of the perfect insect — in 

 short, a full life-history. 



With regard to the structure 

 of insects, it may be repeated, 

 and must always be borne in 

 mind, that an insect is a creature whose body is divided into 

 three parts — head, thorax, and abdomen. As a biological subject, 

 insect anatomy and physiology is a very broad and interesting 





Fig. 9. — Fully developed Tortoisesliell Butterfly. 

 (Flatters & Garnett.) 



