Page:Supplement to harvesting ants and trap-door spiders (IA supplementtoharv00mogg).pdf/56

 the first door the spider ever made, and that the consecutive layers mark successive stages in the enlargement of the nest.

There is therefore a broad distinction as to construction between cork nests and wafer nests; moreover, while the former are, as far as we know at present, all of one type, and only differ in size or proportion, the latter appear under five distinct types.

Thus, every known cork nest, whether found in Europe, America, or the Antipodes, has the same solid door and simple tube; while of the wafer nests, some have branched and others simple tubes, and some again possess a lower door in addition to the upper or surface door.

In the following pages I intend to treat of the trap-door spiders and their nests in the same order in which the latter are placed in the diagram, commencing with those of the cork type B, and then dealing successively with the several wafer nests from C to G. We have already spoken of A, the nest of Atypus piceus, and seen that our present knowledge of this nest, of the habits of its occupant and of those of its relations, is still far from complete.

The cork type is, as my readers will perhaps remember, the great cosmopolitan type which ranges round the world, and which, curious to say, is built by many different spiders belonging to distinct genera.

The idea of planning this very perfect bit of mechanism appears to be the common inheritance of these several spiders, separated though they are by wide intervals of geographical space as well as to structural divergence.