Jeepers Creepers, where’d ya get those multilayered retinae?

A few weeks ago I was fortunate to get a chance to blast down to the White River Hills in extreme southwestern Missouri.  Cicindela obsoleta vulturina (prairie tiger beetle) was my quarry – I had made arrangements to meet up with fellow cicindelophile Steve Spomer (principal author of Tiger Beetles of South Dakota & Nebraska, Spomer et al. 2008) and show him a few of the better sites I had found for this species.  We would have good success due to gorgeous fall weather and perfect timing, and the next day I would be fortunate to extend its known distribution further north and east.  Still, the beetles are not early risers, and I found myself that second morning with some time on my hands while waiting for these sleepy-heads to arise from their slumber and begin their foraging activities.  As I trolled the thinly soiled dolomite exposures of a new site I had identified the previous day, a spot of red jerking erratically through the sparse vegetation caught my eye, and looking closer I was delighted to see this small but brilliantly colored jumping spider (family Salticidae) trying to evade my gaze.

Jumping spiders are perhaps the most diverse of all spider families, but it is their extraordinary visual capabilities and complex predatory and courtship behaviors that they are best known for.  Popular as research subjects, to the rest of us they are simply endearing little animals.  Some of the largest and most colorful jumping spiders belong to the genus Phidippus, which is also one of the most diverse genera in the family and boasts some 60 species in the continental United States (Edwards 2004).  The genus is characterized by details of the eye placement and carapace shape (Richman 1978) but can often be recognized by their relatively large size, numerous erect hairs, and conspicuous iridescent chelicerae just below the front eyes.  The species can be quite difficult to identify, especially the females, but I feel reasonably confident that this individual is a male of the widespread species P. apacheanus.

I wasn’t always so confident – browsing images on BugGuide left me confused after finding images of P. apacheanus and P. cardinalis males that looked almost identical. However, further digging reveals P. apacheanus is characteristically a more intense red, while P. cardinalis is more orangey with lighter bristles which may appear silvery.  Also, P. cardinalis often displays makings on the abdomen – generally a light line running around the anterior part of the abdomen and sometimes tiny light spots on the dorsum – that are absent in P. apacheanus.  (This begs the question as to whether some of the BugGuide photos may be misidentified?)  Another Phidippus species that might be confused with P. apacheanus is P. clarus; however, that species has a black cephalothorax and bright abdominal markings.  According to Herschel RaneyP. apacheanus is most often seen in fall.

This was a very difficult subject to photograph.  He refused to come out in the open, preferring to duck and peek from behind whatever vegetation he could find.  Realizing that my desire to photograph him without any manipulation would be a lesson in futility, I used my finger to prod him towards and onto a small, flat, lichen-encrusted rock, where he would look at me with ever-increasing alarm and try to flee at the approach of the camera.  Lots of failed shots were discarded in the field before I finally got a few I thought I could live with (which, I think, are a decided improvement over my first jumping spider photos).  As I zoomed in for the closeups, I saw for the first time the shimmering of his multilayered retinae moving in the depths of his primary medial eyes.  The retina is the darkest part of the eye, thus, when the eye is at its darkest the spider is looking straight at you!

Photo Details: Canon 50D w/ MP-E 65mm 1-5X macro lens (ISO 100, 1/250 sec, f/13), Canon MT-24EX flash (1/8 ratio) w/ Sto-Fen + GFPuffer diffusers. Typical post-processing (levels, minor cropping, unsharp mask).

REFERENCES:

Edwards, G. B.  2004. Revision of the jumping spiders of the genus Phidippus (Araneae: Salticidae). Occasional Papers of the Florida State Collection of Arthropods 11:i-viii, 1-156, 350 figs.

Richman, D. B.  1978. Key to the jumping spider (salticid) genera of North America.  Peckhamia 1(5):77–81.

Spomer, S. M., M. L. Brust, D. C. Backlund and S. Weins.  2008. Tiger Beetles of South Dakota & Nebraska. University of Nebraska, Department of Entomology, Lincoln, 60 pp.

Copyright © Ted C. MacRae 2010

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About Ted C. MacRae

Ted C. MacRae is a research entomologist by vocation and beetle taxonomist by avocation. Areas of expertise in the latter include worldwide jewel beetles (Buprestidae) and North American longhorned beetles (Cerambycidae). More recent work has focused on North American tiger beetles (Cicindelidae) and their distribution, ecology, and conservation.
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28 Responses to Jeepers Creepers, where’d ya get those multilayered retinae?

  1. Mike Bok says:

    Very nice shots! I photographing my first jumping spider last weekend (he visited us while we were eating lunch, mid-hike), and my results weren’t exactly as spectacular. They are at the size where my reverse mounted 50mm stops giving me relatively acceptable results.

    The eyes of jumping spiders are surprisingly convergent with those of diving beetle larvae. Not only the doubled layered retina, but also its shape. Jumping spiders and diving beetles (and mantis shrimp, because they never want to be left out of a visual modality) both have a very narrow, linear retina that they scan over objects. Whereas the diving beetle moves its whole head up and down, the spiders have muscles that move the retina around within the head.

    http://arthropoda.southernfriedscience.com/?p=1868

    Its pretty crazy how commonly the linear retina has been stumbled upon: Spiders, stomatopods, beetles, copepods, pelagic snails.

    • An interesting contrast between salticids and dytiscids in how they utilize their retinal bands to generate an image. I would think all that head bobbing by the latter would serve as a warning to potential prey, but you can’t argue with diversity!

      My first jumping spider pics weren’t quite so good either – and I even had the benefit of Canon’s 65mm lens.

      • Mike Bok says:

        Maybe the head bobbing hypnotizes the prey, similar to the way chameleons and praying mantids approach their targets. Assassin bug, as well, may disorient their prey into inaction by tapping them on their heads repeatedly as they approach.

        • I wonder if those are stimuli (bobbing, tapping, etc.) that just aren’t detected by potential prey – they’re certainly helpful to the predator for prey location, and with no negative selective pressure against such behaviors… Interesting speculations.

          • Mike Bok says:

            I am not impressed by the prey location or distance detection ideas about the tapping that assassins do. I feel that assuming that the animal doesn’t know how far away its target is sells their visual system way short.

  2. TGIQ says:

    These are really stunning Ted…beautiful shots of a beautiful subject!

  3. jason says:

    Fantastic shots, Ted! Wow! And for an uncooperative subject, you certainly make it look all too easy. As for the identification issue, I’m so glad to read that you had a moment of pause before putting a name with this adorable face. Knowing that from time to time something stumps you makes me feel better about my more common confusion!

  4. Mike B. says:

    That is one heck of a good-looking jumping spider! We mostly seem to have zebra jumping spiders around here in the Northwest- still cool, but not nearly as colorful.

  5. P. apacheanus is the perfect Halloween character! He seems inquisitive, even charming. Oh, those peepers–How they hypnotize!

  6. Kurt says:

    Great shots of this handsome fella, Ted!.

  7. Very awesome shots indeed!

  8. randomtruth says:

    Excellent captures Ted. Funny, but we saw what seems to be the same species just the other day, while out on the Chimineas Ranch.

  9. jtrager says:

    This is an absolutely gorgeous critter Ted, beautifully rendered in you images!

  10. Beautiful spider, Ted! And yes, very fitting Halloween spider too. I recently photographed a small jumping spider in my back yard – very mediocre results because it just wouldn’t stay still. Great job on capturing some great shots – doesn’t matter how many bad ones you toss.

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