In the second number of the current volume of the _Canadian
Entomologist_ is a very interesting account of the discovery of some
small creatures that feed on the eggs of the Tent Caterpillars. It is
very gratifying indeed to the orchardist, to learn that he has help from
any quarter in the work of destroying such pests as these. During the
past summer, the Forest Tent Caterpillar swept over large tracts of
country in the Counties of Perth and Middlesex, stripping the leaves
from the trees in the orchards, as well as from those in the forest, and
doing a vast amount of injury. The question was asked at the Summer
meeting in Stratford, if this pest was likely to continue in such force
in years to come; if so, the out-look for fruit in those parts was
gloomy enough. It was bad enough to have to look after the common Tent
Caterpillar, and keep that in subjection, but such an invasion of its
congener, if likely to be continuous, was fearful to contemplate. The
discovery, to which reference is now made, may help to answer the
question, and to illustrate the wonderful measures adopted to keep in
check all undue multiplication of our insect enemies, and so to preserve
the balance of power.
[Illustration: Tent Caterpillar]
The distinguished editor of the _Entomologist_ was devoting an evening
to the microscopic examination of some cluster of eggs of both the
American and the Forest Tent Caterpillar, when he noticed that in many
instances the gummy covering of the clusters was imperfect; that, here
and there, a piece had disappeared, leaving the eggs bare, and in some
cases the exposed eggs were empty. This circumstance induced him to cut
into the affected clusters, which were found to be colonized by mites.
They had evidently eaten into the eggs and devoured the young larvæ, and
also consumed the missing patches of the glutinous covering. In some of
the eggs the larvæ were found uninjured, while out of others would
proceed several active little mites. Sometimes these mites were so small
that five or more were found in a single egg-shell, with plenty of room
and to spare. These, which he noticed were very active and nearly
transparent, were doubtless young mites, not fully grown. The full grown
mites were much larger, one of them nearly filling the egg-shell; these
were of a pale-red color, with bright red eyes, and sluggish in their
movements. On the outside of some of these egg-clusters, he found tiny
pale-red eggs, which proved to be the eggs of these mites. On nearly
every cluster that he examined, he found more or less of these mites. It
is to be hoped that they are generally distributed over those parts of
the country that have been infested by these Tent Caterpillars, if they
are, they will help vastly in checking their undue multiplication.
As some of our readers may feel desirous of examining the egg-clusters
of these Tent Caterpillars for themselves, we give an engraving, shewing
the cluster as it will now be found, fastened around the twigs of the
apple trees. They will be more easily seen in a cloudy day, and will be
found near the ends of the shoots, not often more than a foot from the
tip, and frequently but an inch or two. The gummy covering will prevent
the individual eggs from being seen quite as distinctly as they are
shewn in the engraving, it having been removed to shew the regularity of
their position. This engraving represents the moth and egg-cluster of
the Forest Tent Caterpillar. Fig. _a_ shews a twig with the bracelet of
eggs upon it, and _b_ represents the moth with the wings expanded.
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