[Odonata-l] black in dragonflies

Thu Dec 6 07:32:11 PST 2007

Hi David: 

Regarding S. striolatum and S. nigrescens....
The two taxa have recently been synonymized based on molecular studies.
Sympetrum nigrescens is considered a dark morph of S. striolatum. The
information is in the following paper:
Pilgrim, E.M. and C.D. von Dohlen. 2007. Molecular and morphological
study of species-level questions within the dragonfly genus Sympetrum
(Odonata: Libellulidae). Annals of the Entomological Society of America.
100: 688-702.

Regards,

Rob

Dr. Robert A. Cannings

Curator of Entomology

Royal British Columbia Museum

675 Belleville Street

Victoria, BC, Canada   V8W 9W2

Phone: (250) 356-8242. Fax: (250) 356-8197

E-mail: rcannings at royalbcmuseum.bc.ca

________________________________

From: odonata-l-bounces at listhost.ups.edu
[mailto:odonata-l-bounces at listhost.ups.edu] On Behalf Of David Goddard
Sent: Thursday, December 06, 2007 4:00 AM
To: Nick and Ailsa Donnelly; 'Bob Glotzhober'; 'Odonata List Server'
Subject: Re: [Odonata-l] black in dragonflies

Hi All,
         Following on from Nick's observations, over here in the UK we
have the question of Common Darter Sympetrum striolatum and the Highland
Darter Sympetrum nigrescens are they the same species but with more
black for the Highland Darter or are they indeed different species.

Regards
David Goddard

	----- Original Message ----- 
	From: Nick and Ailsa Donnelly <mailto:tdonelly at binghamton.edu>  
	To: 'Bob Glotzhober' <mailto:bglotzhober at ohiohistory.org>  ;
'Odonata List Server' <mailto:odonata-l at listhost.ups.edu>  
	Sent: Wednesday, December 05, 2007 8:24 PM
	Subject: Re: [Odonata-l] black in dragonflies

	As an additional note, the more northern members of widespread
species commonly have more extensive black than their more temperate
cousins.  An example that struck me at the time was Enallagma ebrium,
which in Northern Quebec is so black as to cause at least one person
(not me) to think it might be a new species. (not me)

	Nick Donnelly

________________________________

	From: odonata-l-bounces at listhost.ups.edu
[mailto:odonata-l-bounces at listhost.ups.edu] On Behalf Of Bob Glotzhober
	Sent: Tuesday, December 04, 2007 1:38 PM
	To: Odonata List Server
	Subject: [Odonata-l] black in dragonflies

	I am looking for data, opinions, thoughts and ideas on why so
many dragonflies have black as a major color. This initially hit me last
summer when a couple of us locally were working with 3 plus species of
Macromia on the Big Darby Creek near Columbus. Since then, I've been
invited to talk to a bunch of folks as a part of our state's wildlife
diversity conference - and the entire conference theme is "Back in
Black".  Obviously, an emphasis will be around the resurgence of black
bears in Ohio, but also other "black" wildlife including cormorants,
black vultures, the (melanistic) Lake Erie Water snake, and others -
including black dragonflies.

	While my emphasis will be on the diversity of such critters and
their ecology, I want to spend a little time discussing the thought of
why so many are black. To launch things (my apologies to Tom) I am
inserting a communication from Dr. Tom Schultz at Denizen, who has
worked on colors in Odonata before. This is a basic good start - and
maybe it will stimulate some further thought and discussion within this
group. I eagerly await to hear not only hard data but off-the-wall
theories as well. 

	Here is Tom's correspondence:

	"Bob,

	I have given this a little bit of thought.  The combination of
yellow and black is as conspicuous as any Odonate coloration can be,
especially if the visual system of the insect is trichromatic with
sensitivities to UV, blue and green (like bees).  The striping provides
important contrast that enhances detestability; consider the difference
in how C. erronea looks compared to S. linearis when each patrols the
same shaded stream.  In dark forest understory black and yellow would be
the color pattern of choice. In light flecks, yellow is a conspicuous
color  because it reflects the filtered green-yellow light without
matching the green background. However, when flying in and out of light
flecks the broken pattern of Cordulegaster should make it hard to
detect.    

	The eyes may be part of the color pattern that  these
dragonflies use to attract mates or identify themselves, but they should
also boost the reception of the wavelengths they reflect (e.g. green).
No research has really been done on the roles of color in odonate eyes,
but it is a reasonable guess that the emerald green eyes may function
like a tapetum in vertebrates.  

	There are only three studies using electrophysiology to
determine the color vision of an odonate species.  Two bluets are know
to have receptors for UV, blue and green.  It has been shown that one
red libellulid species has an additional  red photoreceptor.

	Tom"

	Bob Glotzhober

	====================

	Robert C. Glotzhober             614/ 297-2633

	Senior Curator, Natural History
bglotzhober at ohiohistory.org

	Ohio Historical Society         Fax: 614/ 297-2546

	1982 Velma Avenue

	Columbus, Ohio  43211-2497

	Visit the website of the Ohio Historical Society at:

	  www.ohiohistory.org and check out our online collections
catalog.

	See or purchase Dragonflies and Damselflies of Ohio or the Cedar
Bog Symposium II at OHS's new E-Store:  http://www.ohiohistorystore.com/

	Visit the Ohio Odonata website at:
http://www.marietta.edu/~odonata/index.html

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