Tarantula – Died from Bad Molt

2013 October 9

This is a rather sad posting. On October 5, 2012, one of Sandy’s oldest tarantulas[1], a Costa Rican Zebra Tarantula, had a bad molt, and died. It was able to get its legs out OK, but the old skin around its abdomen didn’t split like it was supposed to, and it evidently couldn’t breathe.

Molting is a very dangerous time for tarantulas, because they are pretty much at the extreme size limit for land animals with exoskeletons. I understand that bad molts are the primary cause of death for really large tarantulas. When they molt, their new exoskeleton is so soft that for a while they basically have no support at all, and they can easily be crushed by their own weight. And this one was pretty large – in the next picture, that’s a standard 8-1/2 x 11 inch sheet of paper that she’s lying on.

Here’s a shot of the appendage sockets in the skin that she molted. The two at the far right are where her chelicerae (mouthparts) came out, the next two are the sockets for the pedipalps, and the eight sockets continuing off to the left are for her legs.

Here’s her face and eyes.

The eyes aren’t very big, just these little things in a knob on top of her head, and I doubt that she was able to see much beyond moving patches of light and dark. Like a lot of other spiders, tarantulas mostly depend on their sense of touch.

Tarantula fangs are a bit different from most other spiders. Tarantulas are a type of Mygalomorph, which have fangs that face backwards.

This is in contrast to the “True Spiders”, which have opposed fangs that face each other. Tarantulas therefore stab down with their fangs, and clamp their prey against their body.

Her fangs wouldn’t have stayed white like that if she had lived. They would have hardened and darkened, like they were on the skin that she molted off.

It was sad, but she lived a good life for a tarantula. She dug lots of burrows[2], and pounced on a lot of crickets. And that’s what tarantulas do.

[1] Some years ago, we adopted a big tarantula that had formerly belonged to some graduate students who hadn’t been taking very good care of it. Sam really liked it, and so did Sandy and I, and so Sandy learned all she could about keeping tarantulas. And then acquired some more. This one was our second tarantula (the first one is still going strong). She also has a Baboon tarantula, donated a Mexican Red-Knee to the public library as a library pet, and raised a bunch of little Red-Knee spiderlings that she bought online from a breeder. We are very careful with them, because even though they look big and scary, tarantulas are pretty fragile. If they are dropped, they are not only likely to break their legs, but their massive abdomens are likely to have fatal internal injuries.

[2] Costa Rican Zebra Tarantulas are a burrowing species. When Sandy first got this one, she put her in a terrarium with several inches of bedding in the bottom. The tarantula then promptly dug an extensive burrow a couple of feet long – in a single night! We were concerned that it was going to collapse on her, but she seemed to know what she was doing.

4 Responses
  1. Carole permalink
    October 9, 2013

    They do make fascinating pets and are easy to care for.

  2. Bridget permalink
    October 10, 2013

    I’m glad you posted this. My Chilean Rose died a few years ago stuck in the molt position and this is quite possibly what happened to her.

  3. anna permalink
    October 2, 2015

    this is cool and stupied

  4. Andrew B permalink
    May 7, 2017

    Very interesting. Thank you for teaching me ~ I had NO IDEA they were so susceptible to dying due to their “shedding” (molt)

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