The Ant-Lion and its Trap (continued
page 3)
by John J. Ward F.E.S.
It looks down into the hollow of the pit for some
considerable time, as if expecting something to move. Apparently
the curious central object has a fascination for it, and after
a few minutes the ant seems determined to gratify its curiosity,
and it proceeds to test the smooth and steep banks by means of
its forelegs.
The
antlion will shower it's victim with sand to bring it sliding down
into the pit. The moment the ant steps over the edge of the pit the treacherous
sand gives way, and the startled ant stumbles while endeavouring
to regain its foothold, dislodging still more sand, with the result
that it usually finds itself precipitated to the bottom of the
pit, perhaps right into the hungry jaws of the ant-lion grub. Sometimes,
however, it happens that the ant
has so cautiously alighted on the sides of the pit that it detects
the
danger of the unsafe ground on which it is walking, and decides
at once to return. Now, although it may with caution travel downwards
over the sand spread so smoothly
by the larva, yet to turn round, or climb upwards, is a very different
matter, for the sand immediately begins to roll down the banks.
The moment the sand commences to fall, the ant-lion is alert, quickly
hurling showers of sand up the banks, and before the ant realizes
what has happened, it finds itself slipping down the sides of the
pit. It is at once seized by the formidable jaws of the grub, from
which there is no escape, for these organs act like suction-pumps,
absorbing the juices of the prey while they hold it.
Head and mandibles of the antlion
A large spider, or a beetle, when entrapped, proves a more troublesome
captive, and if, before it is seized, its struggles bring down
sufficient sand to allow it to climb out of the pit, it may escape.
It is, however, a lucky insect that survives a visit to the ant-lion's
den.
When the meal is finished, the ant-lion pitches the shrunken skin
of its victim well beyond the borders of its excavation, probably
to prevent future victims from taking alarm. It then proceeds to
repair the damage to its retreat, and again goes into ambush.
The common species here described is found both in Southern France
and in Switzerland, but does not occur in Britain. There are some
three hundred species of ant-lions known to science, of which America
claims at least thirty ; so that they constitute a well-distributed
group of insects, It should be mentioned, however, that all the
species do not dig pitfalls, and, also, that many of them progress
in the usual direction when walking. Probably when more is known
of these insect the backward movement will be found to be associated
with the pit-making habit. Those species which construct no pits
have to capture their prey by hiding in suitable spots until a
victim approaches.
The duration of the life of the larva depends largely on the food
supply, and it may spend two years as a hunter in the grub state.
It then spins a circular cocoon in the sand, in which it changes
to a pupa, or chrysalis. In due course it bites a hole in the cocoon
and emerges above ground as a winged insect, much larger than the
original grub, and, as previously observed, resembles a dragon-fly,
from which it can be readily distinguished by means of its clubbed
antennas.
The END
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