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 
