166 THE CANADIAN ENTOMOLOGIST. 



and Moths themselves, to partake of them. This exertion it is which, in 

 its resuks, assists in the formation of distinct species. To get their food, 

 rest, protection, etc., a certain amount of work has to be done, and to do 

 this work to the best advantage the fmictional systems are impressed. 

 The food even of a caterpillar does not fall into its mouth. With all their 

 apparent helplessness when discovered, it is only necessary to consider 

 how difficult it is generally to find these helpless beings which exert them- 

 selves constantly to avoid observation from their enemies. Insects as 

 well as man have probably much to learn, and are probably learning after 

 their peculiar fashion every day. In particular I have been struck with 

 the conscious way in which insects seem to provide for their escape from 

 observation. They become rigid in their efforts to keep still. I do not 

 think, however, that the " death mimicry " is a tenable theory. It is by 

 the keeping still XhaX the insects seem to me to appear to " feign death," of 

 the existence of which latter they could have no knowledge. Hard- 

 shelled beetles readily tumble to the ground, not caring for the fall, but 

 soft-skinned caterpillars cling tenaciously. They seem to know that they 

 cannot support the shock of a fall, the practical result of which accident 

 I have often observed by finding dead Sphinx larvae on the sidewalks after 

 a storm which had blown them from their perches. Hairy caterpillars 

 stick less closely than naked ones, relying on their bristles to act as 

 buffers, and coiling themselves so as to shield the head, legs and under 

 surface. 



Rivers assist in the dispersion of insects, and in a less degree, perhaps 

 the particular insects we are now discussing. Nevertheless, upon leaves 

 and sticks the eggs of moths are floated on the current, while the com- 

 merce of the water routes and the great ocean itself brings eggs and 

 pupge with the vegetables and fruits which are carried from place to place 

 in boats and ships. In this way the White Cabbage Butterfly has been 

 introduced from Europe, and probably the Currant Borer, Aegeria Tipuli- 

 formis. A bird's-eye view of the continent of North America shows us 

 the elevations of the Rocky Mountains and parallel spurs in the West 

 and the AUeghanies in the East; These mountain ranges stand in the 

 way of the spreading of Moths, which perish in the cold atmosphere and 

 the storms which gather about their rocky summits. Our faunae can be 

 best appreciated by studying the elevation of the land above the level of 

 the sea. Over the vast plains east of Colorado, the same kinds of Moths 

 generally prevail. The canons and valleys of the West, on the other 



