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I hit the jackpot one day (May 28, 2005 to be exact) - this half-dead tree seemed to attract these male wasps by the dozens. So I spent several hours over the course of 2 days shooting the males. Magnificent insects, to be sure, but what I really wanted was a female. I only saw a couple, and they did not hang around to pose, darnit. So I kept going back, day after day, hoping, praying to the Sylphs and Dryads that inhabit my neck of the woods to get a shot of a female... and then, oh boy! I hit the powerball lottery of insect macrophotography. I thrice caught them in the act of depositing eggs deep inside a dead, fallen tree, and once in a live, upright tree. |
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(Above and below)
This early spring wasp drilled her ovipositor
into solid wood (and presumably, laid an egg
onto a prey item) over the course of 4 minutes.
The female wanders over the surface of the
fallen log, tapping the wood with her antennae.
She is "listening" for the vibrations of her
prey target: a larvae of the horntail wasps,
which live inside cells in the wood. This gal
spent a full 10 minutes prospecting before she
began to drill. At this point, her ovipositor is
"fully assembled" and appears as a solid-looking
threadlike structure extending fully 2 inches
behind her.
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As the drilling begins, the wasp raises the
tip of her abdomen until the ovipositor is
perpendicular to the surface, then begins
pushing the tip into the wood. The abdomen
sort of splits open as the two outside
"guides" begin to exert pressure and
separate to loop back on either side of the
abdomen, to allow the abdomen to push closer
to the surface.
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Scientists
are still not sure how the wasp
"drills." It is thought
vibration might be involved but
no one is sure. I suspect the
tip of the ovipositor is sharp
and the wasp forces aside the
"soft" tissue of the wood much
as you would push a needle into
cork - except the wood of living
trees is much harder and denser
than cork, so who knows? It's
amazing, to say the least. And
how does that wasp know exactly
where and when the egg must be
laid? For it must be laid inside
the cell of the alien larvae -
sometimes laid directly on the
body of the prey, where it will
develop and eat the host from
the inside out.
The great Charles Darwin came up
against one of the greatest
tests of his religious faith
when studying the Ichneumonidae
and contemplating their
seemingly evil and cruel ploy
for exploiting other creatures;
he thought the monstrosity too
evil for God to have thought of
it, much less condone it.
He wrote, in
1860, "I own that I cannot see
as plainly as others do, and as
I should wish to do, evidence of
design and beneficence on all
sides of us. There seems to me
too much misery in the world. I
cannot persuade myself that a
beneficent and omnipotent God
would have designedly created
the Ichneumonidae with the
express intention of their
feeding within the living bodies
of Caterpillars, or that a cat
should play with mice." |
The ovipositor is now almost fully inserted,
and the abdomen has opened up like some kind
of ghastly sofa-bed. The ovipositor consists
of 2 "guides" and the actual ovipositor
which slides in between them. The guides are
the two dark thread-like arches at the left
of the abdomen. The ovipositor is emerging
from the very tip of the abdomen where it
intersects the guide assembly. It's very
difficult to tell how she's doing it while
it's happening.
When the wasp senses the tip of the ovipositor in contact with the host larva, she injects the egg through the hollow tube. After the egg hatches, the young ichneumon wasp larva feeds on the horntail larva and then pupates in the wood. When mature, it chews its way out and begins life as an adult. Adult male wasps are adept at discerning wood-chewing vibrations. It is this that attracted the hoards of male wasps to this tree and log to begin with, which in turn attracted me.
This is a close as I got. The camera lens is
about 2 inches from the wasp. I attribute
her cooperativeness to a single-minded
pursuit: reproduction.
A job well done, the wasp withdraws her
ovipositor and quickly makes her escape. My
camera clock shows the whole process took a
litle over 4 minutes. |
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