THE FIELD NATURALIST'S KNOWLEDGE. 65
The association of the Silkworm (Bombyx mori) with the leaves
of the Mulberry tree is known to all, while the caterpillars of other
Lepidoptera luxuriate in the wood of trees. The large one of the
Goat Moth (Cossus ligniperda) delights especially in the soft wood
of the Willow and Poplar. Some of the Black Poplars in my garden
I had cut down, and found them to contain a large number of the
Goat Moth Caterpillar, though until the trees were closely examined
they appeared quite sound.
The dependence of certain groups of insects upon certain groups
of plants, or rather upon their flowers, is well exemplified by the
fact that there are several distinct insect seasons in the year marked
by the flowering of certain plants, during which distinct groups of
insects make their appearance.
Prof. Westwood says of insects :—
" Such as gather honey or the pollen of plants are among the first to proclaim
the approach of spring ; and their appearance may be dated from the blossoming
of certain trees and flowers of common occurrence. Other plants, likewise
accompanied by peculiar insects, blossom later ; and thus we may trace a mutual
relationship throughout the sparkling spring, the leafy summer, and the melancholy
autumn."
When the sallow and the crocus flower, and the tender green of
the gooseberry bushes delights the eye in the early spring, Mr.
Kirby says is the time
" to collect many species of Wild Bees and Diptera, not afterwards to be met
with, and various other insects now begin to emerge from the pupa. Another
and later season is marked by the general blossoming of the Buttercup, accom-
panied by the Marsh Marigold and Ladies' Smock, when you may hunt the
pastures, meadows, and marshes with success, and take some insects that do not
show themselves later. The coprophagus insects are now abundant. Amongst
others, Aphiodius testudinarius, a perfectly vernal species, is now only to be taken,
and usually flying. A third insect season indicated by Flora, and a very prolific-
one, commences with the blossoming of the Hawthorn, when you must desert the
meads for the enclosures. At this time all Nature begins to put on her gayest
attire, and all her insect tribes are now on the alert and fill the air. They are almost
universally attracted by the sweet and lovely blossoms of the plant just named ; so
that by examining them, you may entrap some of every order, and many that during
the year will appear no more. Even many of the saprophagous insects will sip
nectar from the flowers. The umbelliferous plants proclaim the fourth season of
insects, particularly the Wild Carrot and Parsnip. You will scarcely ever fail to
find, if the weather is genial, hymenoptera and dipterous insects of various
genera, especially such as have a short tongue, engaged in collecting the honey
from those plants. Here you may take some of the rarer Chrysidae, Crabonidae,
Cercerides, &c., and occasionally even Coleoptera. The last insect season may
be dated from the general flowering of the thistle tribe. When these are in
blossom is the best time of all to collect the Humble Bees, the Leaf-cutter Bees
F