I find this group to be a never ending source of fascination. Bulging
compound eyes, see-through netted wings, and flight patterns that would
make a Nassau scientist’s head spin make these insects worthy of a second
look. If you’re talking about the bizarre and the wacky, nature has
pulled out all the stops with this group. Don’t believe me – try this
out for size – imagine an animal that copulates by using specialized
abdominal appendages (see
) to
grasp the head of the female while his mate plays a game of twister
contorting her abdomen underneath him to form what odanatologists call
the “Wheel position.” Sometimes this form of sex becomes a little rough
and the males actually pierce the head of the female with its clasping
genital appendages. Scientists can actually use these puncture marks
as a clue to the sex of the insect. If you think the fun stops here
for the female dragonfly think again. Mating in dragonflies is an act
of attrition where many males vie and battle other males in obvious
aerial chase warfare. Watching a male dragonfly perch on the apex of
a sedge stem at the edge of an invisible territorial boundary launching
sorties against other males that dare to cross the transom is truly
entertaining. Many times the loser of the chase eventually becomes the
winner. When a male is fortunate enough to mate with a female who wanders
into his realm his first line of business is to rid the female of any
sperm deposited prior to his advancements. He accomplishes this task
with the aid of a multipurpose penis designed like a shovel with a nozzle
at the end.
He literally uses this genital adaptation to dislodge his predecessors
deposit before he makes his own. Therefore the last one in wins
and passes along his genetic material to future generations. Weird
sex – I would say so!
O.K. is that all I got, a little quip about dragonfly sex. I
wish that was all I could say about this Order, if it was I
could go back to watching the Yankees play in yet another world
series strictly on the basis of extreme capitalism.
So chew on this dragonfly factoid - being small creatures these
guys have to figure out ways to thermo regulate in hot as well
as cold environments. Like sunbathers on a white sand beach
many dragon and damselflies you see hang out on vegetation,
fence wires, ground and rocks fully exposed to the solar waves.
Others can be found adopting a very distinctive position called
the obelisk, in which the abdomen is pointed directly at the
sun (nearly straight up at midday) to minimize the body surface
area exposed to direct rays. Here’s another one for ya – the
blue colors of many darners and damselflies and the red color
of some species of Meadowhawks are subject to reversible, temperature-induced
changes, becoming bright at higher temperatures and dull at
lower ones.
Still not convinced this group of insects is a mind popper –
how about the Green Darner (Anax Junius) whose diminutive size
belies an incredible endurance. This species is able to fly
over 2,000 miles, migrating from Mexico to Canada where they
breed and die. The emergence of a new generation of adults in
late summer and fall make the journey back to Mexico, breed,
and deposit eggs where offspring emerge in spring to repeat
the cycle. Along the way the green darner eats everything in
its path, wasps, butterflies moths, beetles, flies, and resorting
to cannibalism at times - dragonflies.
On at least two occasions biologists have bore witness to darners
attacking hummingbirds, apparently in an attempt to do bodily
harm. I watched this species display a behavior this summer
that I hadn’t noticed in my preceding 43 year existence – swarming.
A group of at least thirty darners were zigzagging back and
forth within a vertical barrier between 3 and 40 feet from ground.
From what I could see the main prey item was mosquito. The photo
I enclosed was one of these guys I netted and put in the frig
for fifteen minutes after which I placed him on a twig for a
quick couple of shots. He quickly warmed up and within minutes
took flight. The swarm I witnessed consisted of all males which
seem to correlate with the accounts of this species. Female
only swarms have never been recorded. According to Sidney W.
Dunkle, author of dragonflies through binoculars, if a female
enters a swarm it will likely be mated with instead of allowed
to feed.
I’ll give you one more nugget about this group and if you’re
still not convinced we got ourselves one hell of a bizarre order
I’ll throw all my field guides in a pile, douse them in gasoline
and strike a match. Have you ever heard of an animal moving
by means of anal thrust, we’ll now you will. When a dragonfly
is a nymph (in its aquatic juvenile state) it can escape would
be predators by quickly filling its abdomen with water and expelling
it anally for a jet propelled burst of evasion!
Dragon and damselflies are a successful group as testified by
the fossil record and will most likely be around for a long
time to come. The next time you walk by a pond or a stream
give these guys a chance to pull out one of their tricks from
the bag of nature’s wonders.
