While the children were playing in a small brook, they found something
entirely new to them, and as usual, came with hands full, shouting, “We
have found something new! Do you know what these are?”
These new treasures proved to be the larvae of the caddis fly in their
stone houses. This little creature is noted for its complete
metamorphosis. The female fly often descends to the depth of a foot or
more in water to deposit her eggs. As the eggs hatch the habits of their
larvae are exceedingly interesting.
They are aquatic, being long, softish grubs, with six feet. The fish are
very fond of them, for which reason they are in great demand for bait.
The angler looks for “cad-bait” along the edges of streams, under
stones, or on the stalks of aquatic plants. One can easily see that
their lives are not free from care and danger, and so to protect
themselves, they are very wise in building cylindrical cases in which
they live during this dangerous period. The different species, of which
there are many, seem to have their individual preference as to the
substance which they employ in building these houses, some using bits of
wood, others shells, pebbles, or straws. They readily disregard these
preferences when there is a lack of the material which they usually
prefer.
Those brought to me were made of different colored pebbles and were very
pretty homes. We counted the pebbles in one of them and found there were
eighty-nine used, and built so securely that it could not be easily
crushed by our fingers. They were all about an inch in length, a quarter
of an inch in diameter and were perfect cylinders with a large pebble
fastening one end; so no fish could catch them unawares. We placed them
in water, where we could watch their development. They never willingly
left their homes, only thrusting the head and a portion of the body out
in search of food.
When about to pass into the torpid pupa state, they fastened their
houses to some sticks and stones in the water, and then closed the end
with a strong silken grating, which allowed the water to pass freely
through their houses, keeping them sweet and fresh. We are told that
this fresh water is necessary for the respiration of the pupa. Thus they
remain quiet for a time until they are ready to assume the imago form.
When that important period arrives they make an opening in the silken
grating with a pair of hooked jaws, which seem to have developed while
resting in the pupa state. They also have become efficient swimmers,
using their long hind legs to assist them. After enjoying this new
exercise of swimming for a short time they evidently become anxious for
a wider experience, and coming to the surface of the water, usually
climbing up some plant, the skin of the swimmer gapes open and out flies
the perfect insect. Sometimes this final change takes place on the
surface of the water, when they use their deserted skin as a sort of
raft, from which to rise into the air, and away they go to new fields
and new experiences. These insects are known as the caddis-fly of the
order Neuroptera, having four wings, measuring about an inch when full
spread, with branched nervures, of which the anterior pair are clothed
with hairs; the posterior pair are folded in repose. The head is
furnished with a pair of large eyes, with three ocelli, and the antennae
are generally very long.
If you know the haunts of this interesting house builder, scatter some
bright sand and tiny pebbles in the water, and when they are deserted,
gather the houses for your collection.
Rest H. Metcalf.