Moulting

A spider grows by replacing its exoskeleton, and it cannot do that in the open. In the days before a moult it stops accepting food, spins a dense silk hammock — usually in the highest corner it can reach — and retreats inside. Then it goes still, sometimes for over a week. This is the stage that frightens new keepers, and it is the healthiest thing the animal does all month.

The rule for the whole period is: do not open the enclosure. Do not lift the hammock to check. Do not offer food. Do not mist directly at it. A spider partway out of its old skin is soft, blind and fixed in place, and a disturbance at the wrong moment is one of the few things that reliably kills an otherwise healthy animal. A front-opening enclosure earns its keep here, because it means routine maintenance never goes near the hammock.

How long depends on size. A spiderling may be sealed in for two or three days and moult every couple of weeks; an adult female can sit for two weeks between moults that come months apart. Give it time before you assume anything has gone wrong.

When it emerges it will be pale, soft and noticeably larger, and it will leave a perfect empty copy of itself behind — legs, eye lenses and all. Leave it two or three days before offering food, because its fangs need to harden first. The first meal after a moult is usually taken with enthusiasm.

The one genuinely bad outcome is a stuck moult, where a leg or the abdomen fails to come free. There is very little to be done once it starts, and almost nothing to be done by intervening. The cause worth guarding against is a spider that went into the moult dry: keep misting a far wall on the usual rhythm right through the pre-moult fast, never at the hammock, and do not let the enclosure run bone dry for a week because the animal has stopped drinking where you can see it. A spider disturbed mid-moult is the second cause. Between them they are most of the prevention there is.