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When a molt is imminent, the spider will stop eating for several days, weeks and sometimes with adult animals even months beforehand. In spiders with urticating bristles (bristles on the abdomen that the spider can throw at an attacker and that cause an itching sensation or even a rash) a molt can be predicted by looking at a bare patch of the abdomen. Usually this bare patch will be of a light brown or orange color. However, when the spider is going to molt, the new and dark bristles grow underneath the old skin and the bare patch turns dark, almost black. This is a sure indication that the spider is going to molt very soon. It should not be fed at this stage any longer until after the molt is successfully completed as food animals like crickets may nibble at the spider while it's molting. When molting the spider is utterly helpless and will most likely die from loss of blood when attacked by a cricket. Also, even if blood loss does not cause death, there may be difficulties in withdrawing the legs from the old skin or secondary infection of the wound.
The molting begins with the spider turning on its back and lying there for quite some time. Nothing seems to happen except for the occasional twitching of a leg (1). During this stage the spider is pumping heamolyphe (the spiders blood) from its abdomen into the prosoma (front where legs and chelicerae are attached). The tension increases until the skin of the prosoma ruptures and the carapace (lid of the prosoma) is lifted. Out come the new chelicerae and the new prosoma (2). More liquid is pumped into the still soft prosoma and the skin of the abdomen ruptures. The now smaller abdomen is starting to pull out of its old skin and the animal starts to free its legs by pumping liquid into the legs (3). The spider continues to free its legs by pumping blood into them and moving and pushing the legs against each other (4,5,6). This is the most difficult part of the molting procedure and weakened animals are in danger of taking too long to free their legs. Then the new exoskelton hardens inside the old skin and this may cause the spider to die with its legs trapped inside the old skin. Once the legs are pulled out the spider will lie on its back yet for a while to recover from the exhausting procedure (7). After a while it starts to move its legs to get the new joints to work properly and finally the spider gets up again and walks about. It is still a little pale and the new exoskeleton is still relatively soft. This means the tarantula will not take any food for a few days after until the chelicerae are sufficiently hard again. The pale white chelicerae can be seen clearly in picture number (6) between the front legs. Within a few days the new exoskeleton will harden, the colors will intensify and the chelicerae will turn dark again.
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