118 SOCIAL HABITATIONS. 
thought that they were merely a kind of fungus or lichen, 
while others supposed that they were the work of some 
parasitic insect. 
When closely examined, these “ spangles” are seen to 
be discs, very nearly but not quite flat, fastened to the leaf 
by a very small and short central footstalk. Reaumur 
set at rest the question of their origin by discovering 
beneath each of them the larva of some minute insect, 
but he could not ascertain the insect into which the larva 
would in process of time be developed. The task of 
rearing the perfect insect from the gall is exceedingly 
difficult, the minuteness of the species and the peculiar 
manner in which the development takes place, being two 
obstacles which require a vast expenditure of care and 
patience before they can be overcome. 
Supposing a branch containing a number of infested 
leaves to be placed in water and surrounded with gauze, 
it will die in a week or two, and yet there will be no 
sign of an insect. If the branch be kept until the 
winter has fully set in, the desired insects will still be 
absent, and the experimenter will probably think that his 
trouble has been thrown away. The real fact is, that the 
little insects are not developed until the spring of the fol- 
lowing year, and that they pass through their stages of 
the pupal and perfect forms after the leaves have fallen, 
and while they are still lying on the ground. 
We now pass from the British galls to those which 
are found in various other countries. A few of the more 
interesting examples are figured in the accompanying 
illustration. 
Should the reader have the curiosity to examine for 
himself the structure of the British galls (as I trust he 
will do), he will find that when he cuts a juicy specimen, 
