382 THE BIOLOGY OF INSECTS 



the largest of beasts of prey. The birds and mammals may, 

 of course, be infected with Mallophaga, Anoplura, and 

 other insect parasites, but there is another possible hfe- 

 connection between birds and small insects. Glaucous 

 Gulls use moss largely in their nest-building, and two or 

 three species of springtails are to be found in the nests, as 

 well as specimens of a midge {Leria septcntriovaUs) and its 

 pupa, found also in similar connection in St. Kilda ; it is 

 suggested that there is definite benefit to the midges in this 

 association as " the warmth of the sitting birds would speed 

 up the flies' development." The presence of large bird- 

 communities is indirectly favourable to an increase in the 

 numbers of many insects, because the droppings of the birds 

 lead to luxuriant gro\nh of the plants in wliich the insects 

 find shelter and food. 



The importance of birds' nests as shelter for insects is 

 well illustrated by the observations of R. L. Praeger and 

 others (191 5) on the natural liistory of The Bills, a group of 

 rocks oft' the Atlantic coast of western Ireland, situated 

 9 miles N.W. of Clare Island opposite the entrance to Clew 

 Bay and 8 miles S.S.E. of Acliill. These islets attaining 

 a height of about 1 20 feet above sea-level are largely wave- 

 washed as well as wind-swept. In addition to the Common 

 Earwig, probably blown over in flight, their observ^ed insect 

 fauna consisted of a single ant, seven beetles, a bristle-tail, 

 and three springtails, most of which were found in the nests 

 of Puflins and Gulls. It is likely that their presence on 

 these remote rocks is largely due to accidental carriage on 

 the feet of birds across " the intervening sea," and aflbrds 

 an example of the manner in which insects are helped by 

 the flight of birds to extend their range. 



Insects, like animals generally, depend either directly 

 or indirectly on plants for their food-supply. Few plants 

 are utilised by insects to a greater extent than oak-trees are ; 

 it has been computed that over 500 kinds of insects feed on 

 oak in various ways. The leaves are eaten by caterpillars 

 of many Lepidoptera, the most notable of which, in our own 

 country at least, is the small Green Bell-Moth (Tortrix 



