The tropical social wasps of the genus Polyhia and its allies build enormous nests. A species which occurs in Ceylon has nests which frequent ly reach a length of six feet. The nest of the Brazilian Polybia seutelaris is a solid closed structure covered externally with rough knobs or angular projections. The nests of another South American species are so regularly shaped and so compact and solid as to look like a stone. oricntalis mixes a considerable quantity of earth with the paper which it uses in its nest, and there is a nest in the British museum from Bahia supposed to be that of a social wasp, the outer wall of which is apparently formed en tirely of earth and is one-quarter or one-half of an inch thick. The comb inside appears also to be formed of clay, and the whole seems an elaborate construction in pottery. Sharp sug gests that it may possibly he the production of a eumenid wasp which has taken on social habits.
The sting of most of the social wasps is very severe, but the wasps themselves are not danger ous except when disturbed. When they are fly ing about they are perfectly harmless unless at tacked or irritated. A person may stand close to a wasp nest without risk if he stands motion less. In fact, a wasp may settle upon a person with no danger of stinging unless some move ment is made.
The solitary wasps belonging to the Vespoidea resemble greatly in habits the solitary wasps ot the superfamily Sphecoidea, although they dif fer in important structural characters. The family Pompilidle is an extensive one, more than a hundred species being found in the United States. They may well be known as the 'spider wasps.' since they all, so far as known, store spiders in their burrows. As a rule they dig burrows in the ground or utilize excavations made by other insects. Some dig their burrows before they catch their spiders and others reverse the process. One species has been seen carefully to bang its spider on the branch of a plant until the burrow was completed. The tarantula killer (q.v.) of the Southern United States is a mem ber of this family. The so-called 'potter-wasps' of the family Enmenida- belong to this group, and construct globular cells of clay o• sand attached to a twig by a narrow petiole. These little wasps store up caterpillars, sawfly and beetle grubs for their young. Each cell is completely filled and contains a single egg of the wasp. The wasps of the parasitic families Sapygithe, Alyzinichp, and Tiphiida•, as a rule, lay their eggs upon the bodies of the larva- of other insects, especially beetle. larvae.
The true solitary wasps of the superfamily Sphccoidea have been divided into 12 families, and comprise many of the most interesting of in sects. They usually construct cells in subterra nean burrows, each cell provided with para lyzed insects for their larva% In their habits the sand wasps or 'digger wasps' are rather typical of the group, e.g. the great digger wasp S'phecius stores the large cicadas or harvest-flies in deep burrows made usually in clay soils. A burrow consisting of a sloping entrance six inches long, turning at right angles and extending for several inches farther and ending in a globular cell an inch and a half in diameter, is previous ly prepared by the mother wasp. Sometimes the main burrow has several branches, each termi nating in a similar cell. After a burrow is pre pared, a cicada is captured and paralyzed by its captor's sting. The cicada is then earried with great difficulty up an trunk of the tree for some distance in order that the wasp may fly obliquely downward to her nest, the weight of the cicada being so great that she cannot fly with it hori zontally or upward. The terminal cell being reached, an egg is laid under the middle of the victim's body, upon which the footless larva of the wasp begins to feed as soon as hatched. In the course of a week the larva spins a white cocoon mixed with earth, and remains through the autumn and winter, transforming to pupa the following spring. Shortly afterwards the adult gnaws through the cocoon and works its way up to the surface of the ground.
The solitary wasps of the family Crabronithe are rather small insects which burrow in soil and sometimes in decaying wood. A great va riety of insects is stored in these cells, each spe cies, however, seeming to have a distinct pref erence. The industry of some of the members of this family is extraordinary. The Peckhams have observed Crabro stirpicola working night and day for a period of forty-two consecutive hours. The 'fluid-daubers,' or mud-wasps, of the genus Sceliphron (formerly Pelopa'us) build cells of mud, frequently in great numbers, in sheltered places, often entering houses and barns for the purpose. Spiders are stored in these cells, as a rule, and a single egg is laid upon the last spider which has been pushed in, and the larva works rapidly, as do other wasps' larva' of this group. The female wasp completes and provisions one cell before beginning another. The sand-wasps of the family Oxybelidre burrow in the sand and provision their nests with flies.