[Odonata-l] Nehalennia color change
dpaulson at ups.edu
Mon May 17 15:39:51 PDT 2004
I just received the recent issue of the Digest of Japanese
Odonatological Short Communications from Naoya Ishizawa, a set of
interesting short articles about Japanese dragonflies translated into
English by Naoya.
In this issue there is a brief paper Changes of the body colour of
Nehalennia speciosa by Hirozi Naraoka. He released teneral
individuals of this species in a cage in his yard with appropriate
Nehalennia habitat and plenty of small insects to eat, and he
documented their changes in coloration with age. The longest survival
of this tiny zygopteran was impressive, 41 days for 2 females and 34
days for a male.
I was equally impressed by the series of color changes shown by his
descriptions and a series of photos of both sexes showing each stage.
Both sexes go through a typical Nehalennia coloration of metallic
green dorsum, blue abdomen tip, and blue-green to yellow-green eyes.
But with age, the eyes get darker and darker above, finally changing
to brown (males) or red-brown (females) above, the females even with
red-brown postocular spots. The thoracic dorsum changes from metallic
green to copper in females. Furthermore, in the oldest females, the
blue at the abdomen tip was replaced by brown. Old females even
showed some pruinosity on the thoracic dorsum and abdomen tip,
something I'd never heard of in Nehalennia.
I haven't seen this degree of change (pruinosity or red-brown eyes)
in North American Nehalennia, and I wonder if anyone else has, or in
N. speciosa in Europe.
This seems like a very good project to pursue with other species of odonates!
Dennis Paulson, Director phone 253-879-3798
Slater Museum of Natural History fax 253-879-3352
University of Puget Sound e-mail dpaulson at ups.edu
1500 N. Warner, #1088
Tacoma, WA 98416-1088
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