Fw: [SoWestOdes] Female Forktail
- Hi! You very well may be right. Definitely the Plains Forktail have
been the most common of the odes around here this spring. I don't have
Walker's book so I can't compare illustrations with photo.
I'm especially interested in your reporting of immature andromorphic
forktail females that show bright red, mate before maturity, and then
migrate. Does Corbet mention this in his book on damselflies? Since
this is a very expensive book, I'm hoping to look at it via library loan.
Citrine forktails, these tiniest fragile little damsels, migrating vast
distances, almost blows the mind. They must be a lot sturdier than I
think they are.
Robert Larson writes:
I was just looking at your forktail female and
comparing it with Walker's illustrations of Ischnura.
Especially the illustration on Plate 20, fig. 3c in
(The Odonata of Canada and Alaska). Due to the thin
humeral stripe and the abdominal markings along with
the large postocular spots yours could be the immature
gynomorphic (heterochromatic) female of the Plains
Forktail (Ischnura damula) as in Walker's 1953
illustration. That is my best guess.
I have noted that several species of Ischnura, in the
immature andromorph females, that there is an early
stage where these females show bright red coloration
to the pale areas and not the typical orange. I have
observed this in Ischnura denticolllis and Ischnura
hastata, and those females are found in copulation
with mature males before the annual monsoon rains
here. According to Corbet this mating of mature males
with immature females is a sign of long-range female
migrants. Also, the population of the andromorph
females appears to decline during the summer months
here in southern New Mexico.
About three years ago I had sent a note to Philip
Corbet about the long-range migrant reproductive
behavior in Ischnura hastata females. He had sent a
note back about Cordero's finds of female I. hastata
on the Azores off of Spain. Evidently, the female I.
hastata are long-range migrants that can reach the
Azores, furtilized or unfertilized, and then reproduce
by parthenogenesis on those islands. From reading the
se-odonata site today I see that Cordero has just
published his finds in (Nautre).
Robert R. Larsen
906 E. Orange St.
Roswell, New Mexico 88201-7440
Regular e-mail: roblrsn@...
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