PRESIDENT S ADDRESS. Clll. 



involuntary impulse as a bright light at night. As to what it is, 

 or how it is generated, we seem to be still in the dark. The 

 tendency to migration is by no means confined to insects, but 

 occurs in many other classes of animals, notably birds ; but even 

 amongst them the cause and object is by no means always 

 obvious. In some cases, such as the locusts, the migration 

 might be set down to the desire for fresh food ; but why should 

 they fly to the enormous distances over which they travel, when 

 they must pass plenty of good feeding places on the way ? 

 Dragon-flies feed entirely on other insects, but they are not 

 likely to obtain them by proceeding in dense columns. It has 

 been suggested that they may migrate, because the ponds in 

 which they were bred, and in which they would naturally lay 

 their eggs, have dried up, and they go in search of new breeding 

 waters ; but I am not aware that there is any evidence that this 

 is the case, and even then it does not explain the concerted 

 action of the swarm, nor have they been seen to make for water 

 as their destination, as far as I know. 



The migrations of butterflies seem to be the most objectless 

 of all, for it can hardly be contended that they migrate on account 

 of the desire for food, as it is very little that they eat (or rather 

 drink) in the perfect state, and that only a little honey from 

 flowers, or water. A more probable desire on the part of the 

 female butterfly would be that of finding the food plant of its 

 larva for the purpose of egg-laying ; but there is no evidence to 

 show that they only migrate from a district when the food plant 

 is scarce, and two, at least, of the greatest migrants, Vanessa 

 Cardui and Colias Edusa, feed on a variety of plants, and would 

 not, therefore, be likely to suffer in this way. Besides this, some 

 of the records of swarms state that they consisted entirely of 

 males. 



We see that a tendency to migration exists, more or less, all 

 through the animal and vegetable world (e.g., the dispersal of 

 thistle down over wide areas), and that it is frequently of great 



