A bright blue tarantula

Have a look at this lovely blue tarantula from Brazil. The species is Pterinopelma sasimai, named after Dr. Ivan Sazima, a Brazilian zoologist who discovered the species in 1971 but didn’t formally name it. He had a blue female which died during molting. Here are two videos:

The species wasn’t in fact formally named until 2011, in a paper by Rogério Bertani et al. in Zootaxa (link and free access below).  Finding it was hard work; as the first link above notes:

The 3 researchers were only able to rediscover the species after 5 years of intensive work, due to the fact the area she lives in is very harsh. All species were found on high altitude with poor vegetation and extreme weather conditions (10-35°C), experiencing periods of extreme precipitation and drought.

The intriguing thing about this gorgeous creature (how many blue spiders can you think of?) is that it is the females who are blue while the males are a drab brown. You can see this from the figure below, taken from the Zootaxa paper (see caption):

(From paper): FIGURES 14─16. Pterinopelma sazimai sp. nov. (14) Female, holotype. (15) Male, paratype. (16) Juvenile. Photos: 14, 16, C. S. Fukushima; 15, R. Bertani.

Here are its habitat and range:

What’s intriguing about the paper on this species, and several descriptions, is that there is no speculation I’ve seen about the big difference in color. (The sexes described as so different in color weren’t really different species, for you can see them mating, as in the video below.) Usually when one sex is brightly colored or ornamented in animals, while the other is less conspicuous, it’s almost always the males who are colored or ornamented. That, of course, is because of sexual selection, which results from a differential parental investment that makes females a scarce resource for which males must compete. So why is the female blue here? Your guess is as good as mine.

Here is a female molting. When tarantulas do this, and they do it throughout their lives, they simply pop the top of their cephalothorax and emerge from it, as if from a tank turret, withdrawing their legs from the old appendages like someone taking off their pajamas. The newly molted animal, which remains quiescent till it hardens, is all shiny and pretty.

When I kept tarantulas at Harvard (I had more than half a dozen, and kept them well fed with crickets and clean cockroaches), I’d see this all the time, and it was mesmerizing.



Bertani, R., H. Nagahama, and C. S. Fukushima. 2007. Revalidation of Pterinopelma Pocock 1901 with description of a new species and the female of Pterinopelma vitiosum (Keyserling 1891) (Araneae: Theraphosidae: Theraphosinae). Zootaxa 2418: 1-18.


  1. Liz
    Posted September 20, 2017 at 2:39 pm | Permalink

    Beautiful color and interesting music.

  2. DrBrydon
    Posted September 20, 2017 at 2:53 pm | Permalink

    Reminds me of the big, neon spider they used to have in “The Haunted Mansion” at Walt Disney World. To my mind the more visible a spider is, the better.

  3. rickflick
    Posted September 20, 2017 at 4:11 pm | Permalink

    Could it be that the brightly colored female results from the reversal of roles in care of the offspring? Maybe the female melts into the bushes while the male attends to the young and so must remain camouflaged. I wonder if some kind of mate selection signaling has been observed that would make the female’s color important.

    • Posted September 20, 2017 at 4:34 pm | Permalink

      That is an interesting idea. I know of no other spider where this is known to happen, though.

    • Posted September 20, 2017 at 5:04 pm | Permalink

      Yes, I think the female not only produces the egg sac but also tends it.

      • rickflick
        Posted September 20, 2017 at 5:28 pm | Permalink

        It’s quite an interesting puzzle.

      • Liz
        Posted September 20, 2017 at 5:46 pm | Permalink

        Wouldn’t it be the other way around if the female has the bright colors?

  4. Posted September 20, 2017 at 6:23 pm | Permalink

    how many blue spiders can you think of?

    There are also several other species of blue tarantulas, such as Dolichothele diamantinensis (originally Oligoxystre diamantinensis). However, in this species there is a “typical” sexual dichromatism, that is males are bright blue and females are brownish.

    Bertani R, Santos T dos, Righi AF. 2009. A new species of Oligoxystre Vellard, 1924 (Araneae, Theraphosidae) from Brazil. ZooKeys 5: 41–51. https://doi.org/10.3897/zookeys.5.83

    Photos: https://commons.wikimedia.org/wiki/Category:Dolichothele_diamantinensis

  5. Mark Joseph
    Posted September 21, 2017 at 12:07 am | Permalink

    Does anyone know if the blue is caused by physics (like from a thin film of oil on water) or chemistry (i. e., some sort of pigmentation)?

  6. Dave
    Posted September 21, 2017 at 4:40 am | Permalink

    We’re regarding the blue female as “brightly-coloured” because we’re seeing her out in the open, in bright light. However, from what I know of tarantulas, they’re nocturnal hunters and spend the daylight hours in burrows or hollow logs etc. In very dim light or total darkness a blue spider may be indistinguishable from a black or dark brown one. In this case, the blue colour might be a by-product of some metabolic process and have no adaptive or social significance at all.

    Also, do we know whether spiders can see in the ultra-violet part of the spectrum? I know that some insects can. Things that look one colour in our part of the visible spectrum can look quite different in UV.

    Just speculations here, but it certainly is a strikingly beautiful spider. I owned a tarantula once, many years ago, but it was a nondescript brown species and nowhere near as prett as this one.

  7. blottootto
    Posted September 21, 2017 at 7:16 am | Permalink

    Coloration in tarantulas is a mystery. They don’t have good eyesight (they can’t distinguish much except for light and dark) so colours probably wouldn’t be for sexual reasons then? Also they’re nocturnal and generally live in burrows so are very rarely out in the open so it doesn’t sound to me like aposematism would be the reason either.

  8. blottootto
    Posted September 21, 2017 at 7:19 am | Permalink

    Oh, the male by the way was originally was misidentified. The male was more recently described correctly in this link. “The true male of P. sazimai is herein described from a specimen collected near the type locality. Similar to the conspecific female, this male has characteristic blue iridescent setae covering the carapace, chelicerae, legs, and palps.”


    • johnw
      Posted September 21, 2017 at 9:10 am | Permalink

      I did a little research as to whether one can purchase one of these (answer = yes ~$40 US for a “sling” = spiderling, which are brown) but noticed that taratula buffs who owned P. sazimai in one arachnid forum were claiming the males are blue as well. Guess they would know. I don’t plan getting one.

      • blottootto
        Posted September 21, 2017 at 9:14 am | Permalink

        Yes, it has been known a long time among hobbyists that the original description was probably wrong since all of our males have been bright blue. (Though not as blue as the original video that JC linked to – that looks doctored somehow or maybe filmed under some type of light.)

        I used to have a P. sazimai sling which unfortunately died of mysterious causes just a couple weeks ago. 😦 It’s one of the rare blue tarantulas that is suitable for the beginner hobbyist.

  9. Posted September 22, 2017 at 12:48 am | Permalink

    Is there any indication of whether the spider fluoresces? I know that fluorescence is exhibited by several brightly coloured arthropod species. The adaptive value of fluorescence is unclear, but there may be some.

  10. Brian salkas
    Posted September 23, 2017 at 5:11 pm | Permalink

    three minutes into the video someone is ripping a bong in the background, or at least thats what it sounds like to me…

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