180 THE BIRD WATCHER 
new activity might wellgrise, which, if fostered, would 
be of advantage to the general commonwealth. But 
let us consider the old ones. Terns, as we have seen, 
are vigorous in the defence of their eggs and young. 
They mob and attack any one—be it bird, beast, or 
man—who trespasses upon their breeding-grounds. 
If, therefore, only about half the colony were needed 
for the nurture of the young, and thus gradually came 
to be the equivalent of the workers amongst ants and 
bees, in the other half there would exist the elements 
of a soldier caste. Of these it would become at first 
the more special, and in time the exclusive business, 
to drive all enemies away from the ternery; and 
since efficiency in so important an office might 
well outweigh the otherwise ill effects of a loss of 
fertility in certain members of the commonwealth, the 
soldiers, both male and female, might, in the continuous 
prosecution of their task, come gradually to lose the 
sexual instinct, which, again, would allow the others 
to lay, with advantage, a greater number of eggs. I 
have mentioned the case of a dog making regular 
daily expeditions to a ternery, in order to feast upon 
the eggs ; and if one dog could commit havoc like this, 
what might not some wild egg-eating species do, if 
not efficiently kept away ? It is obvious that the eggs 
thus destroyed might amount to more in number 
than those by the loss of which they would be saved 
to the community ; and, on the other hand, a caste 
whose sole task it was to guard the eggs and young 
might be competent to guard a greater number than 
