100 Bulletin of the Brooklyn Entomological Society Vol. XIV 
would not be able to take advantage of the developing physical 
ability to invade the new media and regions. It was only when 
these necessary “prerequisites”? were acquired, that the forms 
better equipped than their more conservative “non-metabolous ” 
relatives, were enabled to invade and adapt themselves to new 
surroundings, which their more conservative relatives were not 
fitted to do. It is extremely difficult to comprehend how insects 
not already equipped for invading new surroundings could suc- 
cessfully enter these surroundings and establish themselves there, 
so it would appear that the environment did not produce meta- 
morphosis, but the insects which developed metamorphosis in the 
old environment were able to leave the old conditions and estab- 
lish themselves in new ones. Furthermore, since new habits and 
structures are frequently developed by more or less gradual 
changes in previously existing ones, the structures and traits de- 
veloped in connection with the hiding habit, may have furnished 
a “point of departure” in the development of the ability to enter 
upon a wood-boring, and other new types of existence ;* and the 
differences between the immature and adult stages already quite 
marked in lower insects (Odonata, Plecoptera, etc.) may have 
become more and more accentuated, and the more “ plastic” 
mature stages probably developed more and more adaptive fea- 
tures to be acted upon by natural selection, until complete meta- 
morphosis was evolved, not so much by the direct action, as by 
the selective influence, of the environment. 
_ While it is quite true that larve as well as adults have become 
Vane involves no great feat of imagination to assume that through an 
intensifying of the tendency to hide under stones, logs, loose bark, etc., 
among certain insects, there might eventually develop a tendency to bur- 
row or eat their way under loose bark, or into soft wood, among such 
forms; and the wood-boring habit possibly arose in this way. Similarly, 
the habit of hiding under stones, etc., might lead to a tendency to dig 
under such shelters, and eventually to a tendency to tunnel in the earth. 
Furthermore, the fact that certain Tipulide burrow in the soil, while 
others burrow in moist earth near the water, and still others live in muck 
and water, suggests that these instances may represent possible steps in the 
adaptation to aquatic life on the part of certain water-inhabiting forms, 
although other features, such as adaptations to life in an intensely humid 
atmosphere, etc., were doubtless factors in the development of the ability 
to live in water. 
