PHYSIOLOIGICAL ANIMAL GEOGRAPHY 587 
1. The importance of the breeding instincts and the breeding 
place 
We have shown that the adults range over an area much greater 
than that which the larvae inhabit and that a species is entirely 
absent where feeding habitats of the adults is represented and the 
ege-laying place or larval habitat absent. 
Those tiger beetles which hibernate in situations different from 
the one in which the larvae are found, always return to the breed- 
ing place to deposit eggs. When the breeding place disappears, 
the species also disappears. The larval habitat or egg-laying 
place is much narrower and more definitely circumscribed than 
any other part of the habitat. The breeding place and the breed- 
ing instincts are, then, the center about which all other activities 
of the organism rotate. They are the axis of the environmental 
relations of these organisms. 
a. Comparison with other activities and relations. The breeding 
place and breeding instincts must usually be considered in con- 
nection with the feeding ground, and feeding instincts as well as 
other factors. The tiger beetles will not breed where there is 
not sufficient nourishment for considerable periods. The feeding 
place is often the second consideration after breeding. In the 
tiger beetles, however, the feeding structures and habits are so 
generalized that their food is plentiful everywhere, and the food 
relations need only be mentioned. A third important environ- 
mental relation is that to means and place of escape from those 
environmental factors which tend to destroy the organism, such 
as its enemies, extremes of weather or climate, ete., but all these 
are of secondary importance. 
b. Fixity of breeding instincts. The determination of their 
degree of modifiability or fixity would require experimental work 
which I have as yet been unable to accomplish. There is, however, 
good evidence from field study that the breeding instincts are 
most fixed of all the instincts. Since such behavior characters 
in the tiger beetles are usually specific or racial, they are probably 
modified only by the gradual processes of evolution. 
