THE CHRYSANTHEMUM BLY. 137 
and the lower pair are nearly white, and edged with a fringe 
similar to that which has already been described. 
As a general rule, the leaf-mining caterpillars are 
solitary ; and if even two or three are found in the same 
leaf, each leads an isolated life, and does not inhabit 
the same burrow as its neighbour. There are, however, 
exceptions to this rule, as to most others, and certain 
species of leaf-miners inhabiting the henbane, live har- 
moniously together between the membranes of the same 
leaf. They are larger than the ordinary species, and 
are remarkable for their power of burrowing into a fresh 
leaf when ejected from their former habitation, a power 
which does not seem to belong to the caterpillars of the 
Microlepidoptera. 
Although the greater number of these insects belong 
to the lepidoptera, the rule is by no means an universal 
one. Many beetles are thus parasitic’ within the leaves 
of plants, and, as a general rule, they belong to the 
family of Curculionids, or weevils. There are also 
several species of dipterous insects which have this habit, 
among which may be named the CHRYSANTHEMUM FLY, 
which burrows into the leaves of the flower. There is 
also a genus of flies called Phytomyza, 7.¢., Plant-sucker, 
the different species of which select particular plants and 
burrow between the membranes of their leaves. The 
holly, for example, is infested by one species, the honey- 
suckle by another, and the common heart’s tongue by a 
third. 
We must now glance at a few of the insects that are 
parasitic upon other animals. ‘Their numbers are very 
great, but we must restrict ourselves to those which con- 
struct some sort of a habitation. 
