No. 390.] SECURING INSECTS FROM BIRDS. 481 
struck it on the ventral side so as to disable the beetle, and 
then he hammered it to pieces and ate the soft parts. 
The quick flight of Odonata and many Diptera prevent them 
from being captured in any quantities. I can offer no reason 
why the rose chafer is not a favorite article of bird food. I 
have often found this insect abundant where I have collected 
birds, but, with the exception of the kingbird, no bird seems 
fond of it. Catbirds captive and at liberty avoid the Colorado 
potato beetle. One adult catbird, however, shot where there 
was an abundance of food, had eaten a potato beetle. On the 
other hand, catbirds in captivity relish Déabroctica 12-punctata 
but avoid it when at liberty. I could give a number of other 
examples equally perplexing. 
Conclusions. 
It appears to me that certain writers upon protective adapta- 
tions have identified their specific cases as coming under the 
ban of the theory of protective adaptations in so far as they 
coincide with or do not run counter to a statement of Darwin's, 
in which he says that a necessary deduction from the theory of 
the definite facts of organic nature is that no special organ, no 
characteristic form or marking, no peculiarities of instinct or 
of habit, no relations between species or between groups of 
species can exist, but which must now be or once have been 
useful to the individuals which possess them. This statement 
of Darwin’s has comparatively so little intention and is capable 
of such great extension that it forms a secure bulwark over 
which no armies opposed in the least degree to the theory of 
protective adaptations can ever hope to pass. It is as good as 
saying that every conceivable phase of animal life is a protect- 
ive adaptation (a statement which I cannot deny). But it 
seems to me that there are different degrees of protective 
adaptations — that some are much more effective than others. 
There is need of some standard of the efficiency of protective 
adaptations, 7.e., a measure of their working forces. Some of 
the writers on the subject have led one to suppose that a good 
many protective devices secure almost complete immunity 
