INSECTS OF REVERSED BEHAVIOR. 4OI 



the reaction to anyone of which may be the factor that limits the 

 species to its particular environment. If we consider only ten 

 of the more easily recognized tropisms then in the six physio- 

 logical stages enumerated above we have one hundred and 

 twenty positive and negative possibilities for a reaction to an 

 individual stimulus that might limit the species to a specific 

 h.il.itat. The problem is really much more complicated than 

 this as many more reactions enter and all are more or less con- 

 ditioned by morphological factors. So there is no difficulty at 

 all in accounting for a great variety of factors, any one of which 

 in. iy limit the >pecies to a rather narrow habitat. 



In building the conception in the student's mind of the group 

 ol habitats occupied by all the species of a genus the mind auto- 

 matically picks the most obvious habitat characteristic that is 

 -0111111011 to all the habitats under consideration. If this habitat 

 characteristic, such as Hying temperature for .-Eslnias, varies 

 li-oin habitat to habitat the mind automatically considers each 

 >pecie> delicately adjusted to the exact degree of this variation 

 in its specific habitat. This may not be true at all. And the 

 factor which limits each species may not be the obvious one but 

 some in* on-picuous factor and it may be in each species in the 

 genii- a I'ai tor from a different category. It may be a tempera- 

 ture factor in one, a moisture factor in another, a chemical factor 

 in a third species, etc. Thus graduated generic factors may 

 larijcly be a compound figment of the mind of the observer. 



