Praying mantis preys ruthlessly
Bloodthirsty insect practices cannibalism and strange mating
rituals
By Callan Bentley
Flat Hat Staff Writer
I recall once reading a book about insects. When I read it, I was what you might call a "youngster." As a youngster, I spent my days climbing trees, fighting with my brother, and catching insects. It followed that, of the books I read, a good many were about insects.
One particular book stands out in my mind because it suggested tying a length of string about the neck of a praying mantis, with the other end attached to your bedpost. This way, the mantis would protect you while you slept, as it would catch any mosquitoes that came to you for their midnight meal. What a wonderful idea that seemed to me. Unfortunately, my bed didn't have any posts, and besides, I was afraid of rolling over on my benefactor and squishing it while I slept.
Still, it was an intriguing
thought. The praying mantis is a voracious carnivore, eating all manner of its
insect brethren, and it probably would have protected me well.
There are 600 species of
praying mantis around the world, of which there are two that you are likely
to run into on your walks and jogs around campus. The Chinese Mantis (Tenodera
aridifolia) is a hard insect to miss. Bright green in color, it measures
a hefty four inches from head to tail. It was introduced to this continent in
1869 in the hopes that it would keep pest insects under control. The Carolina
Mantis (Stagmomantis carolina) is a native species, and measures a more
conservative two and a half inches in length.
They both look very similar.
If you have ever seen a praying mantis, then you will know that they have a
pivotable head with very large eyes. They have an uncanny way of cocking their
heads to the side when looking at you that reminds me of a confused puppy.
This appearance is heightened
by the "pseudopupils" in the eyes of the mantis. You may be aware
that insects' eyes are fundamentally different from our own. Each insect eye
has many tiny eyes, called "ommatidia," which scan small sections
of the insect's field of view. All these tiny little areas are compiled into
a mosaic image in the insect brain. Praying mantis eyes have more ommatidia
than any other type of insect, topping the scales with upwards of 24,000 in
each eye.
Picture the ommatidia in
the eye as being like a bunch of paper-towel tubes protruding from the same
central ball. Staring at this mantis eye, you can see down the shafts of some
of these ommatidia, but can't see down others. The dark spot in the center is
what is called a "pseudopupil." It resembles the dark spot in the
centers of your eyes, but does not serve the same function. Our pupils regulate
how much light enters our eyeballs.
The mantis you see on any
given bush around campus will be sporting a pair of greatly enlarged front legs.
While the mantis walks on only four of its six legs, these foremost two are
folded into a characteristic posture that calls to mind pious hands clasped
in prayer. This is where the name "praying mantis" comes from. However,
perhaps the insect's name would better be "preying mantis," as it
is such an effective predator. This homonym had me quite confused as a youngster.
As for the mantises, their
youngsters are born hungry. Since two hundred or so of its brothers and sisters
are being born at the same time, it's likely to make its first meal out of a
sibling. Cannibalism is rampant among the mantises, and it's not restricted
just to the immediate family. If you hatch a mantis ootheca (the foamy egg-filled
mass that female mantises lay in the late fall) in a jar, then you are likely
to end up with only one large mantis left within a few weeks' time since hatching.
They hunt by ambush, staying
still until some hapless bug walks by. The mantis will then lash out in one
fantastically swift motion and capture the other insect in its front claws.
The swift movement has inspired the "praying mantis style" of kung
fu.
The most intriguing thing
about mantises, though, is how they go about making more little mantises. The
male will stalk a female and when he gets close enough, he will jump on her
back. This accomplished, the female reaches over her shoulder and, with a tender
lover's caress, chews off his head. Literally. With the head gone, the male's
abdomen will begin mating movements and then, well, they do it. Amazingly
enough, some biologists hold that the male is incapable of mating if his head
is still attached. The brain apparently sends inhibitory messages down to the
abdomen. Once decapitated, these signals stop, and the mating process starts
up. Even more incredible, a male whose head is eaten before he can mount the
female is still capable (sans head) of walking around the female, climbing onto
her back, and mating. The female continues her meal, eating downwards until
she consumes the last bits of the thrusting male abdomen. When dinner is over,
mating is over.
It may seem like a pretty
stupid thing for a male mantis to do, seeing as how he gets killed and all,
but it actually makes good evolutionary sense. All the nutrients in the male's
body are then incorporated into the female, and hence into their young. The
male's sacrifice ensures that his children will have sufficient nutrition to
start out their lives.
So watch out for our local
mantises. They are going to be common around campus in coming months on bushes
and ivy. And you know what you can do if you catch one? Take it home and tie
it to your bedpost with a length of thread. It will protect you from mosquitoes
while you sleep, all night long: a little green guardian who thinks nothing
of eating its brothers, sisters, and lovers.
Let me know how that works
out for you.