Robert,

That's a fascinating observation. My guess is that the bluets were
just flying over the open water as they usually do, but their numbers
were so great that they formed a visible cloud. I have seen that in
several northern bluet species (Northern, E. annexum; Boreal, E.
boreale; Alkali, E. clausum) when superabundant. I also suspect that
the moving away from the predators was just a normal individual
reaction that you could just as easily have seen in a few
individuals, but it was really obvious because there were so many. I
doubt very much that it could be compared with the cohesiveness and
antipredator function of a fish school (I have been a snorkeler and
scuba diver for many years and have watched innumerable fish schools
from both above and below the water surface).

Dennis


On Jul 15, 2009, at 10:24 AM, roblrsn@... wrote:

>
>
>
> On Monday the 13th after a short visit with the refuge manager and
> refuge biologist I made a quick visit to the Lake St. Francis
> Research Natural Area on Bitter Lake Natioanl Wildlife Refuge here
> in New Mexico. I had stopped to take a quick look at Sink No. 20
> and noticed a blue haze, or smoke over the water on Sink No. 19
> from about 50 ft. away. This turned out to be a bloom of Arroyo
> Bluets (Enallagma praevarum) with many thousands over water on the
> small sink hole giving it a smoke like appearance form 40 to 50
> feet away.
>
> When the Pecos Pupfish (Cyprinodon pecosensis) in the sink would
> jump for them, the bluets would form a dense swirling funnel shaped
> school above the water sruface like a small blue tornado as a kind
> of aerial schooling behavior. I could not tell if the pupfish,
> sometimes jumping 2 or 3 at a time, caught any of the damselflies.
> And, when the Blue-eyed Darners would pass over the water the
> bluets funnel shaped schooling would invert like an inverted
> tornado and move below the darner across the water of the small
> saline sink as the darner moved. Perhaps, a form of defensive
> schooling behavior for this damselfly which is well known in fish,
> but not Odonata
>
> Robert Larsen
> Roswell, New Mexico
>
> [Non-text portions of this message have been removed]
>
>
>

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson@...





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