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SCIENCE OE GARDENING.
290
mischief, in the garden, the greenhouse, and the stove, as the plant-lice : they are
known by their oval foi-m, and whilst young they have short feet, thus bearing some
resemblance to the house-bug ; some species are clothed with white down, and others
look like bro^vn inanimate scales upon the bark : these last avc the Coccus hespendum
L., and ai-e generally found upon the orange, myi’tlc, and camellia. The vine is exposed
to another land (C. vitis Z.), wliich will not live in the open air, bnt sometimes so
abounds upon vines in stoves and greenliouses, that the stems appear covered witli
spots of white cotton. Plum trees are likewise injm-ed by another of these pests (C.
persicamin Reaumur), which is very small (a ) ; when magnified, the upper side (b)
represents a shield, aud the legs are only seen when the insect is turned on its back (c) ;
it is principally found on twigs, and the females resemble small red globules. Mr. lu rb y
(Int. to Ent., 197.) mentions a coccus peculiar to the cun-ant bush : the eggs were of a
beautiful pink, and were enveloped in a large mass of cotton-like web, wliich could he
drawn out to a considerahlo lengtli. The female of another species, found on the apple
(C. m-boi-um linearis 71), has the exact shape of a musscl-shell. The leaves of the oalt
are inhabited by another small species (C. folii quercus R .) {fig. 290. d) ; when magnified,
the i-udiments of wings are seen both in the upper (e) and under (e) sides. Tho
coccus of the beech (C. fàgi) is still more minute, and causes small tubercles to arise on
the twigs {g).
1 6 5 7 . D í p t e r a . Dipterous insects ai-e distinguished by having only two wings ; but
they arc lobed, or slightly divided at their hinder base, so as to represent the additional pair
of wings common to most insects. Tlie tarsi are of five joints ; the mouth is lengthened
into a proboscis armed with lancets ; and there is no anal sting. Dipterous insects, in
general, have neither size nor beauty to recommend them ; yet, fi-om their niunbers, they
hold a vei-y important station, and are designed to can-y on many essential operations in
nature. _ Their larvæ are either aquatic or tcn-estrial ; tho former principally living upon
smaller insects, and the latter drawing sustenance irom decayed animal or vegetable
matter, and thus hastening its removal. In this order we find many species highly
injurious to vegetation, and others that are offensive and troublesome both to man and
beast.
1658. Dipterous insects, more particularly injurious to animals, are tho whole family of
breeze or whane flies (Tabânidæ), bot and gad-flies (ÛS'stridæ), and horse files (Ilippo-
bôscidæ). The first of these are excessively troublesome to horses and travellers during
simmrer ; the valves of their mouths resemble lancets, which they dart into the flesh and
immediately draw blood. The Tabanus ôovînus {fig. 291. I) and the Hæraatôpota
pluviàlis {k) are particularly annoying. Of the bot and gad-flies, there ai-e several
species, each appropriated to a particular animal. Thus, the bot-fly (OE 's tn is Zè'qui
Clark, a, b), in its larva state (c), inhabits the anal passage of tlie horse, and is known
among fai-mers by the name of hots : the clu-ysalis state is passed in the ground, and the
perfect fly {a b) appcai-s in the beginning of August. The gad-fly of the ox (OE'strus
i?ôvis, d) appcai-s towai-ds the end of summer; the lai-væ (e) are called by country
people warbels or wornils ; they are found beneath the skin on the backs of cattle, and
occasion large tumours ; the chrysalis ( / ) , like that of the last species, undergoes its
change in the ground. Sheep are infested by another gad-fly {OE. O'vis, g), the grub
of which (A) takes its station in the frontal sinuses, and when full gro-wn it falls through
the nostrils ; it_ changc.s to a cln-ysalis (/), and in two months becomes a fly {g). The
horse flies (Hipp. equina) {fig. 293. I) cause much distress to hoi-scs in the vicinity
of the New Forest, and handfuls may sometimes be taken off the groins and other pai-ts
not well covered with hair. The sheep tick (Melóphagus ovinus) belongs to the same
family as the last insect, although it is destitute of wings and possesses six legs.
291
1659. Diptd'ous insects, injurious to vegetables in their lai-va state, arc numerous. To
begin with thoso most pernicious in the garden, we may mention that radishes are
devoured hy the larva of a small fly (ilZusca radicum Z. j ; and that cauliflowers ai-c
often attacked by another, which lays its eggs iu that part of the stalk covered by the
earth, and the maggots when hatched, either occasion the plant to wither and die, or
to produce a worthless head. Onions are frequently much injured by the lai-yiB of a
small fly, which Mi-. Kirby has named Scatophaga cepamm; and Reaumur gives tho
history of a fly (Eristalis narcissi) the grubs of which reside within the roots of the narcissus,
and destroy them. CaiTOts arc infested by Psila Rosx, the maggots of which bun-ow
round the outside of the root. Celery is attacked by another species, and the leaves
of the same plant by a second, Tepliritis onopordinis.
1660. The different crane-flies (Tipiilidie) comprise several insects, more or less
desti-uctive, in thcir laiwa state, to the labours of the agriculturist, though not vci-y prejudicial
to the gardener. The lai-gest of these is the Bedicia rivosa {fig. 292. c), known
to countiT people by the whimsical name of gaffer long-legs. Two other species, in
thcii- lai-va state, arc confounded with this under the common appellation of the grub.
The first belongs to Típula olerácea; it is sometimes vciy prejudicial to grass m low
marshy grounds, and sometimes even to grain. In France, it has been known to destroy
the grass in whole districts; and in England, it sometimes cuts off a large proportion of
those wheat crops that have been raised upon clover-lays. The other is the lai-va of
Típula coi-nicina, which, in the year 1813, destroyed hundreds of acres of pastm-e m
Holdcmess. Típula crocata (a ) lives in the same manner, but is much less hurtful.
But no dipterous insect is more injurious to com than a small crane-fly of an orange
colour, named by Mr. Kirby, Ceddomyia tritici (fig. 292. Í). The female, whicli ,s
best seen when magnified {h), introduces its long retractile ovipositor into the centre ot
the whcat-flowcr, and has been kno-wn to deposit twelve of her eggs {d) in a single ear
of the plant. These, being hatched, produce a very small laiwa ( J ) , which, when magnified
{g), resembles a large m ag g o t: it feeds upon the poUen, prevents the imprc^iation
of the gi-ain, and thus frequently destroys a twentieth part of the crop. {Linn. Jrans.)
Rve, in the same manner, is attacked by another fly, though of a different genus (Chlorops