Page:Popular Science Monthly Volume 38.djvu/202

190 A third stage in the development of this defensive industry is represented at Fig. 2, which shows the external tube of Leptopelma elongata. This is simply a lily-shaped tube of pure white spinning-work, rising directly above the burrow, and supported by surrounding foliage. The purpose of this structure has not been positively determined. As able a naturalist as A. R. Wallace has conjectured that it may be deceptive in its uses, its resemblance to a flower attracting to it insects, which are thus preyed upon by the proprietor. Such elevated objects are certainly apt to attract insects, who are disposed to alight upon them without regard to their promise of providing food. But I am inclined to believe that Leptopelma's silken lily serves as a watch-tower from which she can observe the approach of enemies and make good her escape in time. Moreover, I believe that it is possible for her to pull together the sides of the sheeted turret and thus erect a barrier between herself and some of her feebler pursuers.

Another form of defensive industry is presented at Fig. 3, which is the exterior part of the turret tube of Dolichoscaptus inops (Simon). This is about an inch in height, and is composed of mingled chippage and mud, a sort of débris of chopped straw and soil.

A still further stage is shown at Fig. 4, which represents a columnar turret of Dolichoscaptus latastei, several inches high. This resembles the tower of the preceding species, but adds thereto a hinged covering after the manner of a trap-door. This turret is also composed of chippage and débris of various sorts gathered from the neighborhood, and is supported upon the surrounding foliage, which in the drawing is a plant of Lavandula dentata. All the uses to which such an elevated structure can be put are served by this ingenious structure, and, in addition, the trap-door is manifestly intended to defend the inmate from the assaults of enemies.

We come now to the trap-door nests of Nemesia meridionalis, and other species making traps of the wafer type, as so fully