144 BRITISH PLANTS 
Symbiotic Insects.—We have already drawn attention 
to the fact that certain plants make use of resident 
insects as a protection against other insects (myrmeco-_ 
phytes, p. 133). If the under surface of the leaves of the 
lime and beech be examined, small nests of hairs will be 
found in the angles between the veins. In these tiny 
grottoes swarm multitudes of minute insects which may 
possibly perform a service to the plants upon which they 
live by devouring the spores and germs of disease. 
