18 INSECT ARCHITECTURE. 



when it issues from the egg ; and the maggot of the blow- 

 fl}'- is, in twenty-four hours, one hundred and fifty-five 

 times heavier than at its birth. Some hirvge have feet, 

 othefs are without ; none have wings. They cannot pro- 

 jDagate. They feed voraciously on coarse substances ; and 

 as they increase in size, which they do very rapidly, they 

 cast their skins three or four times. In defending them- 

 selves from injury, and in preparing for their change by 

 the construction of secure abodes, they manifest great 

 ingenuity and mechanical skill. The figures on the 

 preceding page exemplify various forms of insects in this 

 stage of their existence. 



AVhen larvas are full grow^n, they cast their skins for the 

 last time, undergo a complete change of form, excepting in 

 the case of ametabolous larvae, cease to eat, and remain 

 nearly motionless. The inner skin of the larva now 

 becomes converted into a membranous or leathery covering, 

 which wraps the insect closely up like a mummy : in this 



a, Pupa ut a water-beetle illijiirophitus) ; b, pupa of Si±inx Ligustri. 



condition it is termed Pupa, from its resemblance 'to an 

 infant in swaddling bands. Nympha, or nymph, is another 

 term given to insects in this stage ; * moreover from the 

 pupa3 of many of the butterflies appearing gilt as if with 

 gold, the Greeks called them Chrysalides, and the Komans 

 Aurelice, and hence naturalists frequently call a pupa 

 chrysalis, even when it is not gilt. AVe shall see, as we 



* Generally to ametabolous pupae. 



