Page:Popular Science Monthly Volume 45.djvu/358

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crease of the envelope to admit of extension, of the tiers, the Chartergi go to work on precisely the opposite plan, first forming new cells and covering them afterward. Taking the bottom of the nest as a starting point, they set cells over its exterior surface, being careful to extend the circumference by a row or two to

PSM V45 D358 Interior and exterior of a wasp nest.jpg
Fig. 3.—Wasp's Nest (Chartergus apicalis), Interior and Exterior.

augment the diameter in proportion to the length, so that the symmetry of the building may not be lost. The walls are then lengthened to include the fresh stage, and the end is closed with a new floor, in its turn to become the ceiling of the next tier of cells when further enlargement is desired. No trace of the addition is visible on the outside of the envelope, which would seem constructed at one stroke.

The other kind of nest of Chartergus is constructed on a straight and upright branch, having no lateral twigs. Its elegance can not be sufficiently admired. Composed of a few cells only, the combs are attached to the branch by means of petioles, or solid masses of wax, keeping the groups in a horizontal and parallel position. They stand one over the other, sometimes to the number of ten, separated by considerable intervals, and so admirably upheld by the petioles that the aid of all pillars or columns is dispensed with. The envelope is a spindle of a single leaf of ligneous paper, most artistic in appearance, being marked with