August was an exciting month for our tarantulas as we had not one, not two, but THREE successful tarantula molts over the course of the month. You may remember from previous Notes from the Lab issues: molting is the process in which an arthropod sheds its exoskeleton in order to grow larger. Most of the time, our tarantulas molt successfully, but if conditions are not ideal, or the tarantula is disturbed during the process, the tarantula can be seriously injured or perish. So three successful molts over the course of a few weeks was a cause for celebration!
Tarantulas molt on a fairly predictable schedule. At MBHI, we keep track of each molt so we can be aware of any behavioral changes that might indicate a tarantula (or any arthropod, for that matter) is getting ready to shed its exoskeleton. As they get older and larger, they molt less frequently. For example, Polly, and many of our older tarantulas molt about once a year. Our spiderlings may molt once every couple months.
A tarantula in pre-molt may stop eating, become lethargic, and the abdomen will darken. Again, if you know a tarantula is getting ready to molt, you can recognize these behaviors as normal and not alarming.
But even tarantulas can be unpredictable. If you watch our Online Bug Encounters, you may remember our episode on molting where we introduced you to Carlos, the mexican red-knee tarantula who lost a leg during the molting process. Losing a leg might sound alarming, but tarantulas are perfectly well-adapted to losing limbs when necessary, and Carlos did just fine on 7 legs.
Carlos is old enough that she tends to molt about once a year. But about 2 weeks ago, Carlos stopped eating, and her abdomen grew dark; all indications that she was preparing to molt again, only a few months after her last one.
Our suspicions were confirmed, when on Tuesday we found a healthy, freshly molted Carlos; with a new leg! Granted, the regenerated limb was a little smaller than the others, but considering it had been lost completely, it was pretty impressive. We had known many insects to regenerate limbs after molting, and knew tarantulas could do it in theory, but this was the first time we had seen it for ourselves. Just another example of the incredible resilience of arthropods.