ECOLOGICAL 123 



are five castes altogether. First, there are the ordinary "kings" 

 and "queens", the males and females, deeply pigmented, big- 

 brained, with large compound eyes, and with well-developed 

 wings which fall off after the mating. Second, there are comple- 

 mental or substitutionary kings and queens, less pigmented and 

 less well equipped than the first type, and with only traces of wings. 

 Third, there are "ergatoid" complemental kings and queens, small- 

 brained, scarcely pigmented, entirely wingless, practically blind, 

 and dwarfish in size. Fourthly, there are the workers, unpigmented, 

 wingless, small-brained, and quite sterile. Fifthly, there are the 

 soldiers, big-headed, small-brained, wingless, with large jaws 

 worked by powerful muscles. In some genera the mandibulate 

 soldiers are represented by small individuals with retort-shaped 

 heads, and with the opening of a large gland at the end of the long, 

 tubular snout. These "nasuti", as they are well called, attack 

 aliens by thrusting their snouts on them and squirting out a jet of 

 colourless secretion which seems to act like glue, binding together 

 the weapons or appendages of the enemy. This is one of the quaintest 

 of the polymorphic types, whose origin is so puzzling. For how does 

 one mother come to have five or more different types of offspring? 

 Before we leave division of labour and its advantages, we must 

 notice the profitable arrangement which often secures a succession 

 of functions in the course of the individual life. This may be illus- 

 trated by a reference to the recent work of Rosch on the apprentice- 

 ship, so to speak, of the hive-bee. By marking individual workers 

 in an observation hive, Rosch was able to follow their gradual pro- 

 motion from one kind of task to another in the course of their short 

 life of a month or six weeks. The young workers, that have just 

 emerged from the pupa stage, are first turned to the task of preparing 

 and cleaning wax cells in which the queen will lay eggs. After a 

 few days they pass, or are promoted, to the status of nurses, watching 

 over the young bees in their cells. To begin with, they tend only the 

 older larvae, supplying them with pollen and honey, but later they 

 are trusted with the younger stages, which require a nutritious fluid 

 secreted by the worker-bee from glands that begin to function at this 

 time, about the tenth day of adult life. When the worker is a fort- 

 night old, more or less, she leaves her nursing work to spend a week 

 in the general service of the hive, cleaning away refuse, distributing 

 and storing food, and so on. Trial flights in the open may also be 

 made, but on these first attempts no pollen or nectar is collected. 

 Finally, at the age of three weeks, each worker undertakes the last 

 of its indoor tasks, that of acting as a guard at the door of the hive, 

 preventmg the entry of strange bees or other intruders. When 

 relieved from this duty, the worker-bee devotes all its remaining 

 life and strength to the arduous work of collecting nectar and pollen 

 from the flowers. Here, too, there may be division of labour, for the 



