HOMES AND DOMESTIC HABITS 263 
miners. The larve of some moths and of many hymenop- 
terous insects live in galls on live plants. These galls are 
simply abnormal growths of plant tissue, and are caused by 
the irritating effect on the tissue of the larve which hatch 
from eggs that have been thrust into the soft plant sub- ° 
stance by the female insects. In the familiar galls on the 
golden-rod live the larve of a small moth, and in the vari- 
ous kinds of oak galls live the young of the numerous spe- 
cies of Cynipide, the hymenopterous gall insects. The tiny 
larve of some of the midges live in small galls on various 
plants. To this last group of gall-making insects belongs 
the dreaded Hessian fly, the most destructive insect pest of 
wheat. 
Among the bees and wasps only a few species, compara- 
tively, are communal or live in communities. But nearly 
all the wasps and bees, whether social or solitary in habit, 
build nests for their young and provide the young with 
food, either by storing it in the nest or by hunting for it 
and bringing it to the nest as long as the young are in the 
larval condition. The “mud-daubers” or thread-waisted 
wasps make nests of mud attached to the lower surface of 
flat stones, to the ceiling of buildings, or in other out-of- 
the-way and safe places. These nests usually have the form 
of several tubes an inch or so long placed side by side. In 
each of the tubes or cells an egg is laid, and with it a 
spider which has been stung so as to be paralyzed but 
not killed. When the young wasp hatches from the egg 
as a grub or larva, it feeds on the unfortunate spider. 
Others of the solitary wasps make nests in the ground 
or in wood, and all of them provision their nests with 
some particular kind of insect or spider. Some use only 
caterpillars, some plant-lice, and some grasshoppers. Simi- 
larly the solitary bees make nests in the ground as do the 
mining-bees, or in wood as do the carpenter-bees, or by 
cutting and fastening together leaves, as do the leaf-cutting 
bees. The bees provision their nests, not with paralyzed 
