102 Beekeeping 



its outward appearance. The small head of the larva grows 

 to adult size, the thoracic segments and the first abdominal 

 segment unite and undergo marked external changes to 

 form the thorax of the adult. The abdomen changes least 

 in external form but marked internal changes occur. This 

 brief category of the vital modifications can give but a 

 suggestion of the changes which the pupa undergoes. All 

 of this occurs in an animal which externally seems lifeless, 

 but the internal changes require such large expenditures 

 of energy that the animal loses weight by the consumption 

 of the food which the greedy larva stores up as fat in the fat 

 body. 



The external changes of the pupa are interesting, even 

 though of minor importance. The compound eyes first 

 change from white to pink by the deposition of a pigment 

 around the rhabdomes of the eye (p. 167) and later this pink 

 pigment is gradually covered by a darker external pigment 

 so that the eyes appear brown and then black. The thorax 

 shows coloration earlier than the abdomen. Toward the 

 close of the pupal period, the outside of the animal becomes 

 covered over with a layer of hard chitin for the protection 

 of the adult and to serve as a skeleton for the insertion of 

 the muscles. The legs and wings originate as hollow bud- 

 like outgrowths on the thorax and after the last moult of 

 the larva these invaginations are suddenly extended by 

 blood pressure. The wings are at first small thin sacs which 

 grow and finally take on the adult form, after which the two 

 sides of the sac fuse and the blood in the sac returns to the 

 body cavity, leaving the wings as dry membranes. 



Length of developmental stages. 



The length of the various stages of development varies 

 among the different types in the hive. The preceding ac- 

 count applies especially to worker bees, which have been 

 most frequently investigated, probably because of the ease 

 of obtaining material. The stages are essentially similar 

 in queens and drones. While the rapidity of development 



