40 
INSECTS. 
make short work of all her rivals. The function of the nurses, as their name 
implies, is to rear the young, and, if necessary, preserve the queens. After the 
males, or drones, have fulfilled their duties, they are massacred in thousands by 
the workers; even the young grubs and pup® being dragged from their cells and 
killed. In many wasp - societies, these matters are, however, more leniently 
arranged, since the males usually assist in the general duties of the colony. Still 
even these exhibit an unaccountable habit, all the grubs and pupae being dragged 
out and slain as winter approaches. Whether the wasps themselves begin to experi¬ 
ence the pinch of hunger, and wish to close mouths which must otherwise starve, 
or what may be the motive for such action, is beyond our ability to guess. Since 
every wasp, save here and there a large female, or queen, perishes at the approach 
of winter, the massacre cannot be justified on the score of prudential social policy. 
Solitary Wasps and Mud-Wasps,— Families Mas arid jE and E umenidje. 
The true wasps may be conveniently divided into solitary and social wasps, 
although there is a more or less complete transition between the two. Of the typical 
MUD-WASPS. 
1, Odijnerus parietum, female, with nest; 2, Chrysis ignitcc ; 3, Polistes galllca, female and nest. 
solitary wasps ( Masciridce ), which are mostly tropical forms, and constitute a link 
between the parasitic wasps described above and the Vespidce, but little is known. 
Some kinds are, however, parasitic, and possibly many may be so. On the other 
hand, the Enmenidce are solitary wasps, which make their nests chiefly in mud- 
walls or sandstone cliffs; some constructing a series of mud-cells in the hollow 
stems of plants, and supplying their grubs with caterpillars for food. A well- 
known European example is the figured Odynerus parietum, a variable insect, 
making its appearance in May and June. The nests are made in holes of old 
mud-walls, or the banks of clay-pits, and are filled with grubs of beetles belonging 
to the family Chrysomelidce, or with the caterpillars of small moths. 
Social Wasps, —Family VesdidjE. 
The members of this group form a link between the foregoing and the true 
bees, since each species includes a fertile female or queen, unfertile females or 
