Friday, July 12, 2013

Transformation of the Mirror Spider

For several years, I have been observing the odd behavior of the Mirror Spider (Thwaitesia sp.) where the "silver-plates" on the abdomen seems to shrink when the spider is agitated (or perhaps threatened), revealing the actual abdomen. At rest, the silver plates expand and the spaces between the plates close up to become an almost uniform reflective surface. That is why I called it the Mirror Spider initially. Note that what I am posting are just field observations.

Note: There is a version of my photo that is being re-distributed on the internet with the watermarks willfully removed, and captioned as Sequined Spider or Australian Stained-Glass Mirror Spider (Thwaitesia argentiopunctata). Note that there has not been any confirmation of the ID, and that this spider was found and shot in Singapore. Re-distribution of the photos is not allowed as they are copyrighted - DMCA takedown notices have been issued for unauthorized usage.

    Mirror Spider (Thwaitesia sp.) - DSC_9429
  1. Mirror comb-footed spider (Thwaitesia sp.)
    A female Mirror Spider (Thwaitesia sp.) when on the move. Note that the silver plates on the abdomen are relatively small and spotty

  2. Mirror comb-footed spider (Thwaitesia sp.) - DSC_7495
  3. Mirror comb-footed spider (Thwaitesia sp.)
    Posterior view shows that the silver plates pretty much covers its entire abdomen.

  4. Mirror spider (Thwaitesia sp.) - DSC_7349
  5. Mirror spider (Thwaitesia sp.)
    When it stops to rest, the silver plates appear to expand, filling up the abdominal surface slowly.

  6. Mirror Spider (Thwaitesia sp.) - DSC_9752
  7. Mirror comb-footed spider (Thwaitesia sp.)
    From above, the spider looks like an art work of stained glass!

  8. Mirror Spider (Thwaitesia sp.) - DSC_9767
  9. Mirror comb-footed spider (Thwaitesia sp.)
    After an hour, the silver plates expanded to fill almost the entire abdomen!

  10. Mirror Spider (Thwaitesia sp.) - DSC_9978
  11. Mirror comb-footed spider (Thwaitesia sp.)
    I continued the observation, and it closed up further. The top view of the Mirror Spider (Thwaitesia sp.) still revealed it's heart-line surrounded by red patches

  12. Mirror Spider (Thwaitesia sp.) - DSC_9986
  13. Mirror comb-footed spider (Thwaitesia sp.)
    To highlight the reflectiveness, I tried positioning the flash all over the place

  14. Mirror Spider (Thwaitesia sp.) - DSC_9975
  15. Mirror comb-footed spider (Thwaitesia sp.)
    This was the closest I got of the silver-plates at their largest. This mirror spider (Thwaitesia sp.) is indeed fascinating!

  16. Mirror spider (Thwaitesia sp.) - DSC_7581
  17. Mirror spider (Thwaitesia sp.)
    Posterior view, showing the tight arrangement of silver plates.

  18. Mirror spider (Thwaitesia sp.) - DSC_7609
  19. Mirror spider (Thwaitesia sp.)
    View from above shows a beautiful stained-glass mirror-like surface!

  20. Mirror comb-footed spider (Thwaitesia sp.) - DSC_7505x
  21. Mirror comb-footed spider (Thwaitesia sp.)
    Side-by-side comparison of the same sub-adult male mirror spider just minutes apart. The plates appear to be gold rather than silver.

  22. Mirror spider (Twaitesia sp.) - DSC_7358_anim_640
  23. Mirror spider (Twaitesia sp.)
    I also made a feeble attempt at animating the change in size of the silver plates, but it was really difficult.

  24. Mirror spider (Twaitesia sp.) - DSC_7550_anim_640
  25. Mirror spider (Twaitesia sp.)
    Another attempt from the dorsal view.

  26. Mirror comb-footed spider (Thwaitesia sp.) - DSC_3104
  27. Mirror comb-footed spider (Thwaitesia sp.)
    This is how the mature male looks like for the species found in Singapore, with distinct black patches forming over its ocular region and lateral edge of the cephalothorax.

  28. Mirror comb-footed spider (Thwaitesia sp.) - DSC_3650
  29. Mirror comb-footed spider (Thwaitesia sp.)
    The male shares similar behavioral characteristics with respect to the expansion of silver plates. This particular specimen appears to have silver plates. It is not known if this varies across individuals.

  30. Mirror comb-footed spider (Thwaitesia sp.) - DSC_3311
  31. Mirror comb-footed spider (Thwaitesia sp.)
    When I visited the Peruvian Amazon in 2015, I also found several mirror spiders with a green abdomen.

  32. Mirror comb-footed spider (Thwaitesia sp.) - DSC_1801
  33. Mirror comb-footed spider (Thwaitesia sp.)
    The male was also green, with additional black patterns on its abdomen.

  34. Mirror comb-footed spider (Thwaitesia sp.) - DSC_1268
  35. Mirror comb-footed spider (Thwaitesia sp.)
    Another male, but this had dark green lateral lining at the edge of its cephalothorax.

  36. Other Spiders with Silvery Abdomen

    Occasionally, I get asked if this mirror spider is the only one with reflective abdomens. The answer is a clear no. Here are some examples of spiders with similar silvery abdomens, and some appear to possess similar expansion behavior as well.

    Big-Jawed Spider (Mesida sp.) - DSC_1434
  37. Big-Jawed Spider (Mesida sp.)
    Mesida belongs to the Tetragnathidae family of big-jawed spiders, and possesses a silvery abdomen

  38. Big-Jawed Spider (Mesida sp.) - DSC_3284
  39. Big-Jawed Spider (Mesida sp.)
    Another Mesida, this time with shrunken silver plates.

  40. Big-jaw spider (Mesida sp.) - DSC_4827
  41. Big-jaw spider (Mesida sp.)
    The plates are really tiny sometimes, and appear gold in some instances too.

  42. Comb-footed spider (Argyrodes sp.) - DSC_3466
  43. Comb-footed spider (Argyrodes sp.)
    Some species of Argyrodes have their abdomens partially covered with silver plates as well. They are kleptoparasites and are commonly found on the webs of other larger spiders to steal their food, especially Nephila sp.

  44. Trashline orb weaver spider (Cyclosa sp.) - DSC_6090b
  45. Trashline orb weaver spider (Cyclosa sp.)
    Some species of Cyclosa have their abdomens almost completely similar silver-like surfaces.

  46. Orb Weaver Spider (Cyclosa sp.) - DSC_4320
  47. Orb Weaver Spider (Cyclosa sp.)
    These Cyclosa have been observed to weave beautiful stabilimenta on their orb webs.

More photos of the mirror spider can be viewed here.

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