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True Bees — Part 12

The other common social wasps found in this country belong to the genus Polistes. They are the long-bodied, black wasps with folded wings and slender abdomens. They are frequently found in houses in the autumn looking for places to pass the winter.

The nest of the Polistes wasps consists of a single comb without any envelope. They are found commonly in country barns, and are also attached to bushes and to the lower surfaces of stones which are slightly raised from the ground. They are generally horizontal in this country, but European species build their combs vertically. Polistes feeds upon caterpillars and also vegetable material as well, and its habits in other respects are very much like those of the other social wasps.

Mr. F. H. Chittenden tells me that he thinks one of these Polistes wasps was responsible for the destruction of the cabbage caterpillars in the center of a large cabbage field near Washington last summer. The wasps would hover about a plant and then alight and walk about it, but finding nothing would continue to the next plant, and so on to the next. In the sunny center part of the field the cabbage caterpillars were exterminated, but in the shady portions next a patch of woods they were present in great numbers. Wasps do not see well. They find their prey more by a sense of touch than by a sense of sight, and as they prefer the sunshine they unconsciously ignored the abundant caterpillars in the shade.

There are tropical social wasps, most of them belonging to the genus Polybia, which build enormous nests. It is said that the nest of a Ceylonese wasp reaches a length of six feet, and with a common South American form the paper is so thick and hard that it resembles thick pasteboard, while the outer layer is so fine in texture that one can readily write upon it with ink and a fine pen.

The solitary wasps of this super-family, although differing in structure, resemble greatly in habits the solitary wasps of the super-family Sphegoidea. There is one large family known as Pompilidae, of which we have many representatives in this country. All of these wasps whose habits are known prey upon spiders. More than a hundred species occur in the United States, and most of them dig burrows in the ground, some of them, however, using readily natural burrows and those of other insects. Some of them dig their burrows before they catch their spiders, and others catch the spiders first; and one species has been seen to carefully hang its spider on the branch of a plant where it would not be disturbed by ants while the burrow was being made, occasionally visiting it in the intervals of work to find out whether it was safe. The habits of several Pompilids have been studied by Mr. and Mrs. Peckham. There is a famous wasp of this family which in the Southwest is known as the tarantula-killer.

The wasps or the family Eumenidae are known as potter-wasps, and store up caterpillars, saw-fly larvae, and the larvae of beetles. They form globular cells of clay or sand which are attached by a small pedestal to some twig. They are filled full of caterpillars in just the same way that the mud-daubers fill their cells with spiders, and a single egg is placed in each cell. Prof. O. T. Mason says that certain beautifully shaped Indian vessels and baskets have precisely the form of these cells, and he thinks the observant aborigines may have deliberately copied the insect design.

There is an interesting genus in this group known as Odynerus. These are small active wasps, usually with one or more yellow bands. They were probably originally borers, but are most adaptive in their selection of places in which to make their cells. They use the old burrows of different bees and wasps, and are fond of using old muddaubers' cells. Ashmead found one species in Florida making its cells in the lock of his front door, and in old holes in a board fence and in old oak galls. Walsh found one building its cell in the cavity of a discarded spool. These wasps also sting caterpillars and store them in their cells.

The insects of several of the families, although resembling in general appearance the other wasps, are probably parasitic in their habits. These are the Sapygidae, the Scoliidae, the Myzinidae, the Tiphiidae, all well represented in this country, and the curious Thynnidae of Australia, South America and Africa. By parasitic we mean that their larvae feed upon or within the living insects instead of such as have been paralyzed by the sting of the parent, or which are already dead. The Tiphia wasps are parasitic upon the big white underground grubs which are the larvae of the May beetles or June beetles, and the larva of Scolia has been found in Europe within the body of another beetle, and Ashmead has found an American Scolia preying upon the larva of still a third beetle.