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RE: [nw_odonata] water mite occurrence

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  • Jim Johnson
    I looked through my photos of non-libellulids and the only one that seems to include a water mite is a Cordulia shurtleffii (American Emerald). I m not
    Message 1 of 2 , Feb 21, 2011
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      I looked through my photos of non-libellulids and the only one that seems to
      include a water mite is a Cordulia shurtleffii (American Emerald). I'm not
      positive it's a water mite, but I'm not sure what else it would be. I didn't
      collect that individual, so I can't confirm it.



      It's funny the things that you can see going through a large collection of
      photos. I have a photo of a Gomphus diminutus (Diminutive Clubtail) in South
      Carolina which has something stuck to one of the front femora. It's reddish
      and bulbous, reminiscent of a water mite, but rather large for a water mite.
      I did collect that individual, so I pulled the specimen out and it's
      actually the head of an ant with the mandibles clamped on to the femur. I
      didn't notice it at the time. I presume the Gomphus pulled the ant's body
      off as it would have been within reach of its own mandibles.



      Jim Johnson

      Vancouver, Washington

      jt_johnson@...

      http://odonata.bogfoot.net/

      http://nwdragonflier.blogspot.com/





      From: nw_odonata@yahoogroups.com [mailto:nw_odonata@yahoogroups.com] On
      Behalf Of Dennis Paulson
      Sent: Friday, February 18, 2011 11:35 AM
      To: Odonata-l
      Cc: NEOdes group; SE odonata; gl_odonata@yahoogroups.com; TexOdes Odes;
      SoWest Odes; Cal Odes; nw_odonata@yahoogroups.com
      Subject: [nw_odonata] water mite occurrence





      Hello, everyone out there.

      We all know about water mites on dragonflies (including damselflies). Those
      are the little red or brown spheres that are attached under the thorax or
      abdomen of the occasional odonate. Sometimes only one or a few, sometimes
      rather substantial masses of them. They are a part of our dragonfly lore,
      and I can't imagine teaching a class or writing a book about dragonflies and
      not including a section on water mites.

      Purely to help a friend with a question, I was wondering how prevalent they
      really are, and I've been shocked to see how few photos I have that actually
      show water mites. I have one collection of digital photos labeled
      "Anisoptera reference," and of 3800 photos, I can find mites on only 7 of
      them (listed below). Maybe a third of the photos are from above, so the
      mites wouldn't be visible, but that leaves a sample of 2400. Out of those,
      we'll assume half of them breed in habitats (streams, bogs, seeps) that
      don't support water mites. I was well into my search before I thought that I
      ought to actually count the photos on which I might have expected mites, but
      I'm still confident that I searched well over 1000 of such photos.

      I realize that water mites are more likely to be found on younger
      individuals, and that cuts the sample down still more, but at least several
      hundred were of individuals young enough to qualify. Of course, mites are
      also present on mature individuals at the water (see below). These photos
      are from all over North America, a few from the New World tropics. It is
      noteworthy that I have done a lot of my photography in Washington state and
      have no anisopteran photos with mites from this state.

      I found none at all on any gomphid, corduliid, macromiid, cordulegastrid, or
      petalurid. Many corduliids and at least some gomphids breed in lakes, some
      of which I assume would support water mites. But I found mites only on
      photos of a few libellulids and a single aeshnid. They seem much less common
      than the picture I had in my mind. One of the exceptions to this was at a
      lake in Missouri, where numerous Libellula luctuosa were so heavily infested
      that it had actually distorted the shape of their abdomens.

      Zygopterans are another story. It's not difficult to find mites on
      damselflies in photos, and I will scrutinize my reference photos eventually.
      Corbet, in his big 1999 book on the ecology and behavior of Odonata, summed
      it up like this (p. 320): "The association between Hydrachnida and Odonata
      is virtually ubiquitous wherever habitats suitable for both taxa exist:
      eurythermic waters that are either lentic or slowly flowing, and permanent
      (usually) or temporary. Hydrachnida do not favor oligotrophic waters.
      Zygoptera appear to be more often parasitized than Anisoptera." He goes on
      to discuss the relationship in detail for several pages, based on some very
      good studies. The only anisopteran genera he mentions are Erythemis,
      Leucorrhinia, Libellula, and Sympetrum. This relationship may be ubiquitous,
      but it's not at all common in Anisoptera, and right now I know of only these
      four genera and the two additional ones, Anax and Tramea, from my photos.
      There are surely published notes and/or photos that show additional ones.

      Having spent the last couple of hours looking through that photo file, I
      would like to ask if anyone has any records of water mites on Anisoptera
      other than in the Libellulidae. Considering that I have great numbers of
      photos of Aeshna from North America, I would say mites are virtually
      nonexistent in those common dragonflies of lentic waters, so I'm curious
      about that family as well. It would be worthwhile to have an updated
      knowledge of exactly which dragonflies (again, only Anisoptera) have been
      seen with mites attached.

      This seems to be another of the many areas of odonatology that could use a
      lot more research. Sorry for the cross-posting.

      Dennis
      -----
      Dennis Paulson
      1724 NE 98 St.
      Seattle, WA 98115
      206-528-1382
      dennispaulson@... <mailto:dennispaulson%40comcast.net>

      SPECIES WITH WATER MITES IN PHOTOS EXAMINED

      Anax concolor immature male Brazil
      Leucorrhinia proxima mature male Minnesota
      Libellula luctuosa immature male Missouri
      Libellula luctuosa mature male Missouri
      Sympetrum internum mature male British Columbia
      Sympetrum semicinctum mature male Oregon
      Tramea abdominalis mature male Brazil

      The two individuals from Brazil were photographed in the hand because they
      had mites.





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