80 THE LIFE-STORY OF INSECTS [CH. 



the pupa the wings and other characteristically adult 

 structures are, for the first time, visible outwardly; 



is the instar which marks the great crisis in trans- 

 formation. The pupa rests, as a rule, in a quiescent 

 condition, and during the early period of this stage 

 the needful internal changes, the breaking down of 

 many larval tissues, and their replacement by imaginal 

 organs, go on. Both outwardly and inwardly 

 therefore, the insect undergoes, at the pupal stage, 

 a reconstruction necessitated by the differences in 

 form and often in habit, between the larva and the 

 winged adult ; and the greater these differences, the 

 more profound must be the changes that mark the 

 pupal stage. 



From the prominence of imaginal structures in 

 the pupa, it is at once seen that the pupa of any 

 insect must resemble the adult more nearly than it 

 resembles the larva. But in different groups of in- 

 sects we find different degrees of likeness between 

 pupa and imago. In a beetle pupa (see fig. 16 c), 

 the appendages feelers, jaws, legs, wings stand out 

 from the body as do those of the perfect insect. 

 This type is called a free pupa. The pupal cuticle 

 has to be shed for the emergence of the imago, but 

 the pupa is already a somewhat reduced model of the 

 final instar, with abbreviated wings and doubled-up 

 legs. A free pupa is characteristic of the Coleoptera, 

 Neuroptera, Trichoptera, Hymenoptera and many 



