Readers’ wildlife photos

Reader Charles Spotts sent us some nice hummingbird photos; his notes are indented:

I have several hummingbird photos here that are from April and May of this year.  I keep thinking that I’ll get some better ones this summer, but I don’t think that’s going to happen now; the weather has been uncooperative to say the least.  By my count we’ve already had fifty 100+ degree days, which is unusual for this zip code.  Maybe some of the pics will meet the standards for Readers Wildlife Photos 🙂  The guy with the bright orange head staring at the camera is a Rufous (Selasphorus rufus)  and the others are Anna’s (Calypte anna).

The Rufous first:

And the Anna’s:

Tongue out!

Reader Pyers sent a dragonfly photo and a question; if you’re a card-carrying insectophile, try to answer it:

Out in the Malvern Hills (just round the corner from where Annie Darwin is buried), Worcestershire, England, I saw this critter, a Southern hawker dragonfly, Aeshna cyaneaI had only my mobile so could only grab a snatched shot. 

He adds a question deriving the photo below:

A poser for you and your readers…
If you enlarge the photo of the dragonfly and look at the right wings you will see that amongst the beautiful tracery of the wing are two black areas, one on each wing, at the front tip. (They are present on the left wings but they are a bit blurred). Any idea what the significance of these areas are? Evolutionary significance? I have enlarged the area in the attached. I have also looked at other photos of the same species and they are present as well.
My own guess, if the spot is present on both males and females, is species recognition.

16 Comments

  1. Jacques Hausser
    Posted August 21, 2017 at 8:12 am | Permalink

    This dark spot is the pterostigma, a colored cello present on every odonate (except Callopteridae). It is thicker than the other cells of the wings and its real function is unknown, some people suggest it has a role in the wing’s dynamics.

    • Jacques Hausser
      Posted August 21, 2017 at 8:13 am | Permalink

      cell, not cello…

      • ThyroidPlanet
        Posted August 21, 2017 at 8:28 am | Permalink

        Sub

        I like questions

  2. loren russell
    Posted August 21, 2017 at 8:15 am | Permalink

    The spot is question is the pterostigma, and it’s present in all odonates [and some other insects]. It’s generally thought to have a mechanical function, eg this citation from Wikipedia: “The purpose of the pterostigma, being a heavier section of the wing in comparison to nearby sections, is to assist in gliding. Without the pterostigma, self-exciting vibrations would set in on the wing after a certain critical speed, making gliding impossible. Tests show that with the pterostigma, the critical gliding speed is increased 10–25% on one species of dragonfly.”

    It certainly would be detected by another dragonfly and perhaps allow detecton of wingbeat frequency. But unlike the colored wing bands in various odonates, not a species-specific signal.

    • Posted August 21, 2017 at 9:44 am | Permalink

      Very Cool! Thanks

    • Posted August 21, 2017 at 9:51 am | Permalink

      This is how i understand it. The benefit of reducing vibrations not only improves aerodynamics but the reduction of vibration also helps prevent wing breakage along the front wing margin.

      • Tom
        Posted August 21, 2017 at 11:30 am | Permalink

        Before I saw Loren Russells comment I had thought that they might be involved as an additional visual aid being visible in the creatures huge compound eye assemblage as forming a recognisabl pattern or shape when the wing beats were properly coordinated.
        Another theory bites the dust!

  3. rickflick
    Posted August 21, 2017 at 8:24 am | Permalink

    I never get my fill of hummingbird shots. Excellent quality.

    • Charles Spotts
      Posted August 21, 2017 at 12:33 pm | Permalink

      Thank you!

  4. Posted August 21, 2017 at 9:52 am | Permalink

    Very good pictures! These are really good pictures of hummingbirds.

    • Charles Spotts
      Posted August 21, 2017 at 12:34 pm | Permalink

      Thank you!

  5. bonetired
    Posted August 21, 2017 at 1:22 pm | Permalink

    Many many thanks everyone for answering my question on the dragonfly.

  6. Heather Hastie
    Posted August 21, 2017 at 1:36 pm | Permalink

    Lovely hummingbird pics!

  7. Posted August 21, 2017 at 2:26 pm | Permalink

    These are all so lovely!

  8. Posted August 21, 2017 at 5:20 pm | Permalink

    Meet the standards? they look pretty good me, very nice. Thanks.
    I took a stab at the question and found (by the commenters) i was in the ballpark… pat on the back! yea.
    The uniform position on the wings made me wonder if it could be about stability in flight.
    Like the blackberry btw, reminds summer is coming.

  9. Diane G.
    Posted August 23, 2017 at 2:55 am | Permalink

    Fantastic hummer shots, Charles! Esp. the one in flight–freezing those wings like that takes great skill!

    Cool dragonfly, and great observation, Pyers.


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