And yet even the most complicated form of nest—namely, that of the branched double-door type—is perfectly reproduced in miniature by these tiny architects, with the upper door, lower door, main tube, and branch (fig. B, [Plate IX.], p. 98).
In order to test whether the doors are enlarged or not I measured the surface doors of seven double-door nests and one minute cork door on April 30th, making a careful plan of the terrace wall in which they lay, in order to make sure of finding them again on my return to Mentone in October.
The following table will show that all were enlarged, the average rate of increase being 17/10 lines in the five and a half months which had elapsed:—
| Measured April 30, 1872. | Measured Oct. 18, 1872. | |||||||
| No. I. | 9 | lines across | No. I. | 101/2 | lines across | |||
| II. | 4 | " | II. | 51/2 | " | |||
| III. | 41/2 | " | III. | 51/2 | " | |||
| IV. | 4 | " | IV. | 41/2 | " | |||
| V. | 2 | " | V. | 3 | " | |||
| VI. | 21/2 | " | VI. | missing | ||||
| VII. | 1 | " | (the cork) | VII. | 2 | lines across | ||
| VIII. | 5 | " | VIII. | 71/2 | " | |||
We can scarcely venture from such limited premises to draw any precise conclusions, but if we suppose that during the entire course of the year the nests increase on an average by about four lines in diameter, and assume that the rate of growth continue the same, the nest of the infant spider, whose surface door measures scarcely a line across, would still require four years to attain the dimensions of some of the largest double-door nests, whose surface doors measure sixteen lines across.
It seems to be the rule with spiders generally that the offspring should leave the nest and construct dwellings for themselves when very young.
Mr. Blackwall,[86] speaking of British spiders, says:—"Complicated as the processes are by which these symmetrical nets are produced, nevertheless young spiders, acting under the influence of instinctive impulse, display, even in their first attempts to fabricate them, as consummate skill as the most experienced individuals."
Again, Mr. F. Pollock[87] relates of the young of Epeira aurelia, which he observed in Madeira, that when seven weeks old they made a web the size of a penny, and that these nets have the same beautiful symmetry as those of the full-grown spider. Those of the latter are vertical, circular, made of about 250 feet of thread, having about 35 radial lines and 38 concentric circles, the outermost of which is some 20 inches in diameter. After the lapse of a day or two the web loses its adhesive property and a new one is made. In about six months the female Epeira has completed her ten changes of skin, one of which takes place in the cocoon, and "at the end of eight months the spider is 2700 times as heavy as at its birth." This Epeira lives, we are told, for about eighteen months.