RE: [nw_odonata] water mite occurrence
- 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.
From: email@example.com [mailto:firstname.lastname@example.org] On
Behalf Of Dennis Paulson
Sent: Friday, February 18, 2011 11:35 AM
Cc: NEOdes group; SE odonata; email@example.com; TexOdes Odes;
SoWest Odes; Cal Odes; firstname.lastname@example.org
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.
1724 NE 98 St.
Seattle, WA 98115
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
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