612 EVOLUTION OF ANIMALS Part V 



Different stages of developing eggs fill each tubule of the ovary. They are 

 supplied with nourishment from cells in the wall of the egg tubule, ultimately 

 from the blood. As the oldest eggs mature they slip into the oviduct and in the 

 egg-laying season this becomes distended with eggs. By that time each egg has 

 a thin shell with a minute pore in it (micropyle) through which the sperm cell 

 may enter. As the eggs pass into the vagina they come to the opening of the 

 spermatheca which in a mated grasshopper is crowded with sperm cells. 

 Pressure on this sac forces out the sperm cells and fertilization of the eggs 

 follows. 



Just before fertilization the number of chromosomes in the eggs is reduced 

 to half their former number (Chap. 6). A comparable reduction in chromo- 

 some number also occurs in the sperm cells. Thus, after the male and female 

 nuclei have joined, the fertilized egg begins as a new individual that will have 

 the same number of chromosomes present in the body cells as in those of one 

 or the other parent. 



Egglaying and Winter Life. The grasshopper begins laying her eggs in late 

 summer or fall several days after mating. She digs a short tunnel in dry ground 

 and deposits the eggs shrouded in a sticky secretion. In common grasshoppers, 

 development begins immediately and continues for about three weeks (Fig. 

 30.19). By that time the six legs, the antennae, eyes and the segments of the 

 body all show clearly in the still unhatched embryo. It then enters a rest period 

 (diapause); consumes little oxygen; growth stops and is not resumed until 

 spring. 



The Honeybee — A Flower-insect 



Honeybees are social insects, with each bee a team worker taking a par- 

 ticular part in the life of its colony — an organized society. Honeybees are 

 wholly dependent upon flowers for nectar and pollen, their only food. Great 

 numbers of plants, among them the fruit trees, are in turn dependent upon 

 bees for cross pollination and the consequent continuance of their species. 



Content of the Colony. Honeybees, Apis mellifica, were introduced into this 

 country in colonial times and are now widely distributed in apiaries and as 

 escaped wild bees that build their nests in hollow trees. The colony in a bee- 

 hive has continued to be essentially a copy of the nest in the hollow tree. In 

 summer, there may be 60,000 or more bees in a colony, but fewer in winter. 

 There are three easily recognized castes, the females, workers and queen, and 

 the males or drones (Fig. 30.20). ^ 



The workers constitute the great bulk of the colony — the honeybees that 

 are usually seen on flowers and going in and out of their hives. They are 

 sexually undeveloped females, highly specialized as workers for the general 

 welfare of the colony. They rarely produce eggs and when they do the eggs 

 are unfertilized and develop into males only. Workers are so called because 



