PHYLUM ARTHROPODA. INSECTS 



251 



mals band together for mutual defense, or 

 congregate in one place for breeding pur- 

 poses, or are attracted to a limited area 

 because of the presence of food. Birds are 

 often gregarious during the breeding season 

 and migration. Certain mammals unite in 

 herds partly for protection; for example, 

 male bison, when attacked, form a circle 

 around the cows and calves. The more com- 

 plex societies involve division of labor; the 

 principal types of activity are ( 1 ) reproduc- 

 tion, (2) obtaining food, and (3) defending 

 the colony. Many of the most interesting 

 examples of social life occur among the 

 wasps, bees, ants, and termites. 



Wasps and bees 



Wasps and bees may be solitary or social. 

 Solitary wasps and bees dig a hole in the 



ground or in wood, or construct a nest of 

 mud. Wasps provision their nests with cater- 

 pillars or other arthropods that they have 

 paralyzed; and bees provide pollen ("bee 

 bread") to furnish proteins for the growth 

 of the larvae. After laying an egg in the nest, 

 they close the entrance and give their off- 

 spring no more parental care. 



Bees 



Bumble bees (Fig. 129) and honey bees 

 (Fig. 150) are types of social bees. The 

 fertilized queen bumble bee lives through 

 the winter. In the spring she lays a few eggs 

 in a cavity in the ground, from which 

 workers develop. The workers are infertile 

 females. They carry on all of the activities 

 of the colony except laying eggs. At the end 

 of the summer, males (drones) and fertile 



Larva Pupa 



om 



Larva fed 



"royal 



jelly" 



Portion of 

 honeycomb 



Larva fed 

 "bee bread" 



Larva fed 

 "bee bread" 



Drone (from 



unfertilized egg) 



Infertile 

 female 

 v/orker 

 Figure 150. Life cycle of the honey bee showing growth stages and three adult castes, consist- 

 ing of worker, drone, and queen. Cells of honeycomb in nature are arranged parallel to floor 

 of hive. 



