ASPECTS OF KINETIC EVOLUTION 2 1 9 



tion, perhaps, of a better appreciation of the fate that is already 

 befalling ns. 



Another highly specialized animal, the fig insect, affords an 

 equally instructive illustration of the possibility that a character 

 may develop past the point of fitness, and become dangerous to 

 the species. The fig insects are much too highly specialized 

 to be able to lead a free existence. They live only in the fruits 

 of fig trees, which may very properly be said to have domesti- 

 cated them as their only means of securing cross-fertilization. 

 The two species, the insect and its fig tree, have thus a mutual 

 interdependence of a very complete kind. In addition to their 

 physical peculiarities, the female insects have the highly special- 

 ized instinct to find the young fig fruits and to force their way 

 into them, often with much difficulty and the loss of their wings, 

 so that further flight is impossible. The utility of the insect 

 depends finally upon the fact that it is stupid enough not to dis- 

 tinguish between the male and female fig trees. The difference 

 is a fatal one for the individual insect, for those which enter the 

 female figs are lost. Their eggs never develop, and they leave 

 no progeny, the perpetuation of the species devolving upon the 

 relatively few insects which happen to reach male instead of 

 female trees. Young male flowers are extremely scarce at the 

 time when the principal generation of insects emerges, as though 

 to definitely force them to carry pollen to the female trees. 



It is evident that the continued success of this method of pol- 

 lination depends upon a very acute adjustment of the intelli- 

 gence of the insects. They must know enough to seek, enter 

 and fertilize the fig flowers, but not enough to distinguish be- 

 tween those of the male and of the female trees. All of the 

 insects which are really useful to the fig species in enabling it 

 to ripen its seed are lost to the insect species, for their eggs have 

 no chance of development. From the standpoint of the insect 

 species there is an acute natural selection in favor of those which 

 go to the flowers of male trees, but if there should anywhere be 

 developed an instinctive preference for the male trees so that 

 the fruits of the female trees remained unvisited, the fig would 

 cease, in that region, to produce seed, and would become ex- 

 tinct, along with its insect tenant. 



