THE CYCLE OF LIFE 427 



bugs, Tectocoris lineola, var. banksi. The mother sits in a 

 brooding attitude over her eggs for three weeks, until the 

 young are hatched out. She does not have anything to 

 eat during these weeks. When the young begin to break 

 through the egg-shells, the mother backs away for an 

 inch or so from off the egg-mass, and remains there for 

 some hours, long after the last egg is hatched. She then 

 departs, leaving the young bugs, whom she has perhaps 

 saved from Ichneumon flies, to fend for themselves. 



It is among birds and insects that we find the highest 

 development of parental care, but what a contrast there is 

 between the two expressions. Among insects the prepara- 

 tions that are made for the young are for the most part 

 instinctive, and the mother is often without the satisfaction 

 of even seeing her offspring for she is dead before her eggs 

 are hatched. Among birds, while instinctive behaviour 

 continues, it is associated with much more intelligence, 

 and the preparation of nest-making is followed up by the 

 patience of brooding, and that again by often prolonged 

 nurture, and even education. Many birds are careful in 

 turning their eggs and in keeping the nest clean after the 

 young ones are hatched. Of the nests of birds, what shall 

 we say? so many of them express a climax of art (both 

 intelligent and instinctive) on the one hand and of instinc- 

 tive altruism on the other. For artistic quality, take the 

 nest of the wren, of the thrush, of the chaffinch, of the 

 house-martin, of the bottle titmouse, of the tailor-birds, 

 and of the weaver-birds. Or consider the single case of 

 the sea-swift, which achieves the impossible by fashioning 

 a firm nest out of the juice of its mouth. For altruistic 

 quality, take MacGillivray's fact that he got 2,379 feathers 

 out of the nest of the long-tailed tit, or the burrowing of 



