Page:Popular Science Monthly Volume 53.djvu/678

658 sticks from one to four inches long, in the center of which the lower end of the silken bag protrudes, free from sticks and very flexible; it has a charming silky softness, and is of a gray, ash, or mouse color; of this beautiful tissue the upper or head extremity is also composed, forming a tube half an inch wide.

As a larva grows, needing more accommodation, it splits the habitation at the sides, weaving into the opening portions of the vegetable substances selected, and adding to the exterior fresh pieces of stick, straw, or leaves, as it requires. So with Saunders's case moth, when any accident happens to the nest, the caterpillar, with incredible expedition, repairs the damage received, employing the same silky stuff to fill up the hole, and with a nicety so perfect that the severest scrutiny can not detect what was the extent of the injury.

Under the protection, then, of the substantial and somewhat formidable case the larva lives. At each end there is an opening, and through the anterior one it emerges to feed and change its position. Commonly it only protrudes the head and the first three or four segments of the body, or sufficient to use its six true legs for locomotion when feeding; and if wishful to remain quiet, it usually takes the precaution of fastening a portion of the edge of the aperture by fibers of silk temporarily to the branch upon which it is, that, if alarmed, it can suddenly recede completely into the case, very rapidly drawing in the flexible part after it, by means of its mandibles and fore legs, and contracting the aperture, so as to exclude all enemies; thus hid, it stays in security, suspended only by a few threads. Were the nature of the hanging, tight-closed, strong, tough sack unknown, it would never be suspected of containing an active, voracious larva. Exceedingly wary and timid are these insects in retreating at the approach of danger. On a desire for removal the suspending threads are bitten off close to the case.

As long as the caterpillar is small, and the house of no great weight, it is borne nearly erect; but soon, as a rule, the incumbent mass lies flat, owing to increased weight, and is dragged along in that attitude. The abdominal and anal legs of the larva are furnished with a series of small points or hooks, with which it moves in the tube, laying hold of the interior of the lining, to which it can adhere with great pertinacity; so firm the hold retained, it is impossible to remove the creature without injury.

Having attained full growth, and being about to change to pupa, the larva of Metura Saundersii firmly fixes itself, by means of silken fibers spun for the purpose, to a branch or trunk of a tree, or