2i6 THE DRY-FLY MAN'S HANDBOOK 



crowded in clustered eyes. Mandibles are the upper 

 or strong pair of jaws, and maxillcB the lower or 

 weaker, and the jaws of insects generally open and 

 close laterally. The upper lip is called the labrum 

 and the lower lip the labium. The feelers attached 

 to the jaws are called palpi. The maxillse carry 

 feelers called the maxillary palpi, and the labium 

 other feelers known as the labial palpi. 



The changes in outward form through which an 



insect passes after its birth, 

 Incomplete prior to becoming an adult, are 



metamorphosis. called metamorphoses. Nymph 



is a term applicable to the 

 young of insects with incomplete metamorphosis. 

 Insects of which the immature forms nearly resemble 

 the adults, only differing from them in minor detail 

 and requiring such further development as the 

 unfolding of the wings or the loss of temporary 

 organs peculiar to early stages of life, are said to 

 undergo incomplete metamorphosis. 



Complete metamorphosis is undergone by insects 



when their form at birth bears 

 Complete meta- no appreciable likeness to 



morphosis. their adult form. The young, 



whether with complete or in- 

 complete metamorphosis, are generally voracious, and 

 grow rapidly, changing their skins from time to time 

 as their growth necessitates. In the former case a 

 rest stage then intervenes, during which there is 

 a total cessation of feeding. When the frame of the 



