HOMES AND DOMESTIC HABITS 263 



miners. The larvae 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 larvae 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 larvae of a small moth, and in the vari- 

 ous kinds of oak galls live the young of the numerous spe- 

 cies of Cynipidce, the hymenopterous gall insects. The tiny 

 larvae 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 



