The Life of the Fly; With Which are Interspersed Some Chapters of AutobiographyFabre, Jean-Henri
Science
The Life of the Fly; With Which are Interspersed Some Chapters of Autobiography
Fabre, Jean-Henri
Diptera; Flies
Lucilia Caesar is larger than L. cadaverina and also more forward in her
business. I catch her in labor on the 23rd of April. She has settled
in the spinal canal of a neck of mutton and is laying her eggs on the
marrow. For more than an hour, motionless in the gloomy cavity, she goes
on packing her eggs. I can just see her red eyes and her silvery face.
At last, she comes out. I gather the fruit of her labor, an easy matter,
for it all lies on the marrow, which I extract without touching the
eggs.
A census would seem important. To take it at once is impracticable: the
germs form a compact mass, which would be difficult to count. The best
thing is to rear the family in a jar and to reckon by the pupae buried
in the sand. I find a hundred and fifty-seven. This is evidently but
a minimum; for Lucilia Caesar and the others, as the observations that
follow will tell me, lay in packets at repeated intervals. It is a
magnificent family, promising a fabulous legion to come.
The greenbottles, I was saying, break up their laying into sections. The
following scene affords a proof of this. A Mole, shrunk by a few days'
evaporation, lies spread upon the sand of the pan. At one point, the
edge of the belly is raised and forms a deep arch. Remark that the
Greenbottles, like the rest of the flesh eating flies, do not trust
their eggs to uncovered surfaces, where the heat of the sun's rays might
endanger the existence of the delicate germs. They want dark hiding
places. The favorite spot is the lower side of the dead animal, when
this is accessible.
In the present case, the only place of access is the fold formed by the
edge of the belly. It is here and here alone that this day's mothers
are laying. There are eight of them. After exploring the piece and
recognizing its good quality, they disappear under the arch, first this
one, then that, or else several at a time. They remain under the Mole
for a considerable while. Those outside wait, but go repeatedly to the
threshold of the cavern to take a look at what is happening within and
see whether the earlier ones have finished. These come out at last,
perch on the animal and wait in their turn. Others at once take their
place in the recesses of the cave. They remain there for some time and
then, having done their business, make room for more mothers and come
forth into the sunlight. This going in and out continues throughout the
morning.
We thus learn that the laying is effected by periodical emissions,
broken with intervals of rest. As long as she does not feel ripe eggs
coming to her oviduct, the greenbottle remains in the sun, hovering to
and fro and sipping modest mouthfuls from the carcass. But, as soon as a
fresh stream descends from her ovaries, quick as lightning she makes for
a propitious site whereon to deposit her burden. It appears to be the
work of several days thus to divide the total laying and to distribute
it at different points.
Public-domain text, read in full here on John Shaqi.
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