Page:Supplement to harvesting ants and trap-door spiders (IA supplementtoharv00mogg).pdf/101

 *plexity and subtlety of their contrivance, and, therefore, to the difficulty we experience in properly understanding and describing them.

It will be seen by a reference to Plate XIX., figs. A and A 1, that in addition to the cylindrical branch, which mounts upwards, there is a shorter branch which leaves the main tube on the opposite side (on the left as seen in the Plate), and takes a downward course. Now this descending branch, which is barely more than an inch in length, is a cavity of variable form, being sometimes cylindrical, and sometimes egg- or even watch-shaped, but there is one particular in which it never varies, and that is the position of its elliptic orifice. This orifice is always situated on the opposite side of the main tube to that on which the ascending branch leaves this latter, so that the whole nest, when seen in section, presents the figure of a St. Andrew's cross, only with arms of unequal length.

But the most remarkable point is that, when the lower door is pushed across so as to close the main tube (as shown in fig. A, Plate XIX.), it will invariably be found to lie in such a position that its lower extremity exactly meets the lower lip of the orifice of the descending cavity, when it will be seen that the semi-cylindrical surface of the lower door then coincides with, and appears to continue and form part of, the lower wall of the descending cavity