I own a wild-caught Chilean rosehair tarantula. Unknown to me or the seller, she had mated and was carrying eggs. About a month after I got her, I watched as she excavated a burrow in her cage, which is floored with about 3 inches of commercially-prepared dirt mix. She would gather up balls of dirt about 1 inch in diameter and use her pedipalps (small leg-like appendages near her fangs) to carry them to the opposite end of the cage. (She definitely carried them, rather than rolling them.) She used this method to create a burrow 2 inches in diameter and 5 inches long over a period of 3 days. She also used her pedipalps to carry her white egg case (which also was about 1 inch in diameter). Wherever she moved, she kept the egg case in her pedipalps, except when she was actively hunting.
Given a spider’s proportional strength, I would think lifting a pebble or a small rock during burrowing would not be unusual.
FYI: This was a Mailbag item, not one of Cecil’s columns. As such, this thread will be moved to the appropriate message forum, Comments on Mailbag Answers.
Tarantulas (and their relatives the trap-door spiders) are exceptional, and I did NOT intend to include them in with regular spiders. Sort of like comparing sharks to regular fish - there are LOTS of differences. The major differences in this case are that (1) tarantulas have fangs that operate differently from regular spiders (more restricted range of movement), and (2) tarantulas cannot carry things with their spinnerets. They are FORCED (if you will) to use their pedipalps to carry things, since they have no other body structures which can accomplish the feat. It does not surprise me to find that they can carry soil, or even rocks, but I’m sure that’s not what the person who posted the original query was referring to. Ordinary spiders aren’t going to be using their pedipalps in this manner.
I know this thread is a bit old but I would still like to add my 2 cents.
I understand that true spiders can’t carry rocks and Doug has given a great explanation to this fact. What I have a bit of a problem with is that you purposely didn’t include tarantulas and trap door spiders in your answer. Even though they might not have applied to the question asked, I think they still could have as many tarantula species are native to the U.S.
It just surprised me to read a definite no as an answer as I know it to be possible. I have quite a few tarantulas myself (21) and many have carried balls of dirt, pebbles and small rock while excavating or “redecorating” their enclosures.
I guess I would have liked to see a note saying that some tarantulas CAN carry rocks instead of an outright no.
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