64
THE INTER-RELATIONS OF
is entirely unvolcanic, the Island of Capri being composed exclu-
sively of Cretaceous limestone. As might be expected, the flora of the
one area is conspicuously different from that of the other, and no less
than 57 genera of plants growing on the Vesuvian area are absent from
the island, while the luxurious and high quality of the fruits, especially
of the grape vine, on the volcanic soils are widely famous, and the
rich wines produced on the Vesuvian land are altogether different
horn the comparatively thin Capri wine.
BOTANY AND ENTOMOLOGY, ORNITHOLOGY AND
GENERAL ZOOLOGY.
Botany and Entomology.—There are so many good Botanists
and Entomologists amongst the Members of the Essex Field Club
that the connection between plants and insects must be well known
in this Society, not only generally but specifically, and indeed
no one with any powers of observation can be unacquainted with
the dependence of certain species or genera on the prevalence of
certain plants.
When the distribution of insects is regarded on a large scale,
their geographical extension will be found to coincide, and be quite
in accordance with that of plants. Where there are no plants
there will be no insects, and where there is the most luxurious vege-
tation there will swarms of insects most abound. Where vegetable
life is meagre and stunted by a rigorous climate the insects are dull-
coloured and small, and where the plants are large and the flowers
brilliant, there the insects are large and display the most splendid
colours. The Rev. Dr. Walker reports that no butterflies are to be
found in Iceland, and that the moths are small and dull-coloured,
while, as everybody knows, amidst the tropical luxuriance and
splendours of Amazonian forests, the butterflies are multitudinous,
large and gorgeous, with brilliant colouring.
In detail, too, insects are intimately connected with plants, and
some species may almost be called the parasites of certain plants.
There are three species of Aphidae well-known to be respectively
dependent on three trees, Aphis rosae on the Rose tree, Aphis quercus
on the Oak, and Aphis fagi on the Beech. The cochineal insect
(Coccus cacti) is dependent on a Cactus called the Mopal (Cactus
cochenilifer) and the ancient dye that was used for the curtains of the
Tabernacle and the old Flemish Tapestries was derived from Coccus
ilicis, that fed on the Ilex or Evergreen Oak.