Sharp spines, strange sex

Micrathena schreibersi from Suriname [Canon 1Ds MkII, Canon 100mm macro, two speedlights Canon 580EX]
I know many arachnophobes; in fact I live with one. But being afraid of spiders of the genus Micrathena is about as rational as being afraid of a diamond brooch. These animals are jewelry come alive, harmless, and each more ornate and vividly colored than the other.

There are about 100 known species of Micrathena (Araneidae), most of which are found in tropical areas of Central and South America. Females of these beautiful spiders can barely walk on their own if accidentally knocked off their orb, where they spend their entire life suspended upside down. Because their venom is weak and they cannot run away from danger, they protect themselves by covering their bodies with hard, sharp spines. In one extreme case, females of Micrathena cyanospina have spines that can be nearly 50 mm long. This probably can turn the act of  swallowing of such a spider by a bird or a lizard into the animal’s last meal.

The biology of most Micrathena species is completely unknown, but several, including three that occur in the US, have been studied in some detail. What we have learned about them shows that Micrathena have a really strange sex life. To begin, males are tiny compared with the females, and often the female is ten times as large as the male. They also differ greatly in their appearance, with the females being colorful and sedentary, whereas the males are usually dull-colored and constantly on the move. Both sexes have double copulatory organs, and for some strange reason after the first copulation, when only one set is used, the male must dismount the female and seduce her again before the second copulation can take place. But a lot of things can go wrong during that time, and often another male moves in on the action, and wins the second copulation, which appears to be more significant in the insemination process.

Micrathena clypeata from Suriname [Canon 7D, Canon MP-E65mm macro, Canon MT-24EX twin light]
Micrathena cyanospina from Suriname [Canon 7D, Sigma 15mm f/2.8 EX DG, Canon 580 EXII speedlight]

12 Comments Add yours

  1. Michael L. Draney says:

    Piotr, that Micrathena clypeata is currently my world’s favorite spider photograph…just gorgeous! Thank you for sharing your work with the world, its just a magnificent body of work.

    I wanted to mention that the spines are often not terribly long or stout, and my understanding is that they may primarily function against parasitoid wasps like mud daubers that want to stuff them into cavities and feed their young on them. I’d heard that the spines make the spiders artificially wide, and the wasps avoid these spiders (which are otherwise tempting, as they hang out in their webs during daytime) because they won’t easily fit into reasonable sized wasp holes. I don’t know if I’ve seen experimental evidence of that, I can’t remember where I heard it. Interesting idea, though.

  2. Isaac Mallol says:

    I’m still learning about wildlife photo, and this spider is my constant sorrow, I have tried in different ways, and never get a good picture of it. Only once and I feel horrible wrong as I pace the spider on a leaf, where the picture is “fake” to my eyes and for who ever know this species.
    My problem is to have all the spider focus (spines included), while standing in the web, and don’t get the background completely black, as the Micrathena that I find all the time here at Ecuador are black with some white and yellow ornamentation, but mainly black, so if I try to have the all animal on focus by increasing the F, the final result is a dark picture where the spines get mixed with the dark of the background. If I take down the F, the picture is only sharp in the animal’s head, or one of the spines etc… this is my frustration spider!!!
    I don’t know if must be a material mistake, I’m really new with the camera, and I don’t money for gear, I use a Canon 50D and Canon EF-S 60mm f/2.8 Macro with a ring flash (that I use holding it with my left hand).
    I just realize that I need a third hand to hold a big leaf at the background.

  3. Caine says:

    Thank you so much! It will take some time to do this, but I will definitely let you know when it’s finished, with links to photos.

  4. Caine says:

    Fantastic! I would dearly like permission to try and translate the photo of Micrathena cyanospina to embroidery on canvas, for personal purposes only.

    1. Yes, please use the photo. (But I would really like to see the result when you are done!)

  5. Sean McCann says:

    Spider sex….That is what my girlfriend is studying, and it can be extremely frustrating! Experiments can take up to 6 hours or more…For 1 replicate!
    Nice shots of these weird orbweavers! I always had a hard time getting all of these guys in focus.

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