408 INTRODUCTION TO ZOOLOGY chap. 



The Pupa. — When the time for pupation comes, the nurses 

 either bury the full-grown larvae in the earth, or cover them 

 with particles of earth, and each larva then proceeds to spin 

 a silk covering round itself, which is the cocoon (Fig. 312, C). It 

 accomplishes this by pressing its lower lip against the earth 

 and fixing there a silk thread, which issues from the opening 

 of the spinning gland on the lower lip. It then draws the 

 thread out, and moves its head from side to side, until it 

 has lined the whole of the cavity around it with a web of 

 silk ; after this it straightens its body and rests. 



The workers now uncover it, and carefully pull away all 

 the earth particles, leaving the larva surrounded only by its 

 yellowish-white cocoon of silk. The larva within soon throws 

 off its larval skin, which is pushed to one end of the cocoon, 

 and if the cocoon is removed the pupa is seen with all the 

 parts of the imago clearly visible (Fig. 312, P); the body 

 gradually darkens, the eyes becoming very black ; when 

 it is fully developed, the workers cut up the cocoon on one 

 side and help out the new young ant, still rather pale and 

 weak, and known at this stage as a " callow." 



A " callow " receives at first a good deal of attention. The 

 workers help her to unfold her legs, and they clean and feed 

 her, but as soon as her skin has darkened and hardened 

 she is left to shift for herself. She does not, however, leave 

 the nest till she is several days old. 



The time passed in these various stages, and the time taken 

 to complete the development, vary a good deal according to 

 the temperature, and, therefore, according to the time of the 

 year. Those larvae hatched in the spring become adult ants 

 in a few weeks, whereas those hatched in the late summer 

 spend the whole winter as larvae. 



Males and Females. — In midsummer, some of the eggs will 

 develop into winged ants, most of which are males, though a 

 few are females or young queens. The factors which cause 

 apparently similar eggs and larvae to develop so differently 

 have not yet been determined, although it has been 

 shown that underfeeding seems to be correlated with 

 "worker" structure. There is no proof, however, that 

 further differentiation into special kinds of workers, or the 

 development of males and females, is due to special feeding, 

 such as is thought to obtain amongst honey-bees. Indeed 



