132 MANUAL OF ANIMAL BIOLOGY 



opment of the egg of a Bee is similar to that of the Grass- 

 hopper. 



Metamorphosis. Before finally reaching the adult condition, 

 Insects typically pass through a regular series of developmental 

 stages, two types of which may be noted : (1) incomplete met- 

 amorphosis, such as was noted in the case of the Grasshopper, 

 and (2) complete metamorphosis, which occurs in the higher 

 orders of Insects, including the Hymenoptera to which the Bee 

 belongs. The four stages in the metamorphosis of the Bee are 

 known as the egg, larva, pupa, and adult. They may now be 

 considered in the order named. The eggs, which are laid by the 

 queen in specially prepared cells, are small, oblong bodies of a 

 rather grayish color. After a few days there develops from each 

 egg an elongated, worm-like organism, the larva. The larva, 

 corresponding to the nymph stage of the Grasshopper, is the feeding 

 stage, and during the early part of this period the embryos are 

 supplied with a highly nutritious brood food which is formed by the 

 workers as a secretion from well-developed pharyngeal glands. 

 Later a mixture of pollen and honey constitutes the food of the 

 worker-larvae. Certain of the workers serve as nurses for the 

 larvae, and see to it that the latter are supplied with a plentiful 

 amount of food. The larval period lasts about five or six days, 

 during which time the young embryo increases a great many times 

 in size. Since the exoskeleton of a larva is chitinous and rigid, it is 

 necessary that this be shed periodically and replaced with a larger 

 size as growth proceeds. This molting, which takes place five times 

 while the young Bee is in the larval stage, is of the same character 

 as in the other Arthropoda. 



At the end of the larval period, when a certain size has been 

 reached, each embryo proceeds to spin a cocoon around itself. 

 The cocoon is formed by the secretions of certain specialized spin- 

 ning glands which open near the anterior end of the body. The 

 secretion, which is given off as a liquid, soon hardens, and the 

 young Insect thus encases itself in a silky covering, the cocoon. 

 The final (fifth) larval molt then occurs which inaugurates the 

 'resting' pupa stage. No food is eaten during this time, and the 

 animal inside the cocoon is practically rebuilt. The result is 

 that the elongated worm-like larva is metamorphosed into the 

 adult flying Insect. This remarkable process of metamorphosis 

 takes about thirteen days for the workers and drones, but con- 



