184 : THE DICTIONARY OF GARDENING, 
Insects—continued. 
generally observed by gardeners and agriculturists. Such 
a knowledge frequently enables us to devise means of 
warding off the damage that would otherwise be un- 
avoidable, and of assailing the destroyers in the most 
effective way. 
The following details of structure have reference only to 
mature Insects: 
Mouth. In its essential structure, the mouth consists 
of certain parts, six in number, though some of them 
bear appendages. These parts may undergo great modi- 
fication, and may be adapted to very different uses, so as 
to be hardly recognisable when compared with the mouth 
of one of the more typical forms. The chief modifications 
will be treated of under the various groups of Insects; 
it is here only necessary to describe the parts of the mouth 
of a Beetle, selecting this as a type because of all the 
parts of a fully-developed mouth being well seen in 
Beetles. In them, the mouth is formed by an upper 
lip (labrum), two pairs of jaws working horizontally 
like the blades of scissors (called mandibles and maxillæ, 
or upper and lower jaws respectively), and a lower lip 
(labium). The mandibles are specially adapted for cutting 
the food to be taken into the mouth. The maxill~ are 
not so strong, and often bear tufts of hair to serve as 
brushes. Hach also bears a jointed body (palpus), which 
seems to serve as a sense-organ. The lower lip bears a 
pair of similar jointed bodies (labial palpi). 
Limbs. The middle division of the body (thorax) bears 
the limbs, viz., three pairs of jointed legs on the lower 
surface or breast, and two pairs of wings, attached to the 
upper surface of the two hinder of the three rings of which, 
closely consolidated, the thorax is made up. The legs 
are generally present, though, in some Insects, one or more 
pairs may be ill-developed, or even entirely absent. They 
vary in relative size, and in the number of parts of which 
they are made up; but they are of less importance in 
giving characters for the orders than are the wings. The 
latter organs, in their typical condition, e.g., in Hymeno- 
ptera or in Lepidoptera, are two pairs of broad membranes, 
supported upon nervures traversed by breathing-tubes 
(trachex). The upper or front pair almost always exceed 
the lower or hind wings in size and in complexity of 
neuration, but resemble them as regards texture and general — 
appearance. In several groups, however, this typical 
structure is departed from, as will be more fully stated 
below. Not a few Insects either have the wings small 
and utterly inefficient (as the female Winter Moth, see 
Fig. 294), or altogether absent (as Fleas and many other 
parasitic Insects). 
‘Periods of Destructive Activity. As a general rule, 
i the larve, during their rapid growth, are far more 
hurtful to vegetation than are the perfect Insects; in 
fact, certain of the groups of Insects are unable, in 
the perfect state, to feed upon plants, save by sucking 
up the nectar or honey contained in the flowers, e.g., the 
_ whole group of Lepidoptera. Yet these same Insects, 
in the larval stage, were once provided with strong jaws, 
well fitted to cut their food, and then probably fed vora- 
ciously upon their food-plants. But among the groups 
provided with a mouth suited for chewing (e.g., Beetles 
and Orthoptera), or for puncturing the tissues of plants 
and sucking the-juices (Hemiptera, particularly Aphides), 
the perfect Insects may be almost as destructive as the 
larve ; indeed, some kinds are not injurious to man ex- 
cept in the mature condition. 
General methods of prevention and of remedy against 
damage from Insects, may be treated of here; but 
details as to these practices must be sought under 
the special headings. The methods employed to pre- 
ent attacks must depend on the habits and modes 
of life of the Insects to be dreaded. Of course, the 
destruction of the creatures, either as larve, pupæ, or 
_ mature Insects, before they have laid their eggs, is the 
Insects—continued. 
- most certain means. This may be effected either by 
direct efforts, such as hand-picking, or applications of 
poisonous solutions or gases to them; or else — and pro- 
bably with greater, if less apparent, success—by making 
use of the natural means of checking their undue in- 
crease. Among the most efficient of these natural means 
are birds and parasitic Insects, both of which destroy 
vast multitudes of the more hurtful kinds in all their 
stages. Much has been written, and earnest have been 
the disputes that have heen waged, regarding the relation 
of birds to agriculture and to gardening. While some 
writers have represented them as frequently most de- 
structive to the crops and to fruit-trees, others have as 
strenuously upheld their great value as natural guardians 
of these crops and fruit-trees from the ravages of swarms 
of Insect foes. In these, as in so many other disputes, 
the truth probably lies between the extremes: but, while 
admitting, as we must admit, that birds are, at certain 
times of the year, more hurtful than beneficial to farmers 
. and gardeners, yet the danger from them at these times 
may be comparatively easily guarded against; while the 
benefits conferred by them, during the rest of the year, 
are so great as far to outweigh any damage done by 
them. It must be remembered, moreover, that injury 
is done only by those birds that feed on fruits or seeds, 
such as blackbirds, sparrows, and many finches; or on 
roots or tubers, such as rooks; and that even these 
birds almost all feed largely on Insects also. On the- 
other hand, many species of slender-billed birds may be 
said to live exclusively on Insects throughout the year, 
or such part of it as they spend with us. Some birds, 
like the bullfinch, are in the habit of pulling off the young 
buds of the fruit-bearing bushes. and trees; but this 
seems to be done in the search for larve hidden in 
the buds, and which, if left in them, would destroy 
them in any case. In like manner, the apparent injury 
done to trees by woodpeckers boring into the trunks, is 
not really such, as the holes are bored by the bird to- 
reach and to extract the larvae of Insects hidden away in 
tunnels in the wood, or between the wood and the bark, 
_ and which, if left there, would have done no less injury ; 
while, if they had reached maturity, they would: have re- 
— their kind, to the further detriment of the 
ees. : 
Even more efficient than the birds, in reducing the 
numbers of the injurious kinds of Insects, are the parasitic 
species of Insects; though, from their small size and unob- 
trusive habits, they are readily overlooked, and the work 
done by them undervalued. Among these, some devour the 
Insects or suck out their juices as food. As examples of 
these may be noted the Ground Beetles, and the larve of 
Fic. 292. LARVA OF LADYBIRD. 
the Ladybird Beetles (see Fig. 292) and of the Lacewing 
Flies, which devour the Green Flies, or Aphides, in myriads. 
Other insects (e.g., some Solitary Wasps) carry’ off small 
Caterpillars, &c., to serve as food for their offspring. But 
far ‘more important than even these are the parasites that 
deposit their eggs upon or in the body of some Insect, 
generally a larva, there to disclose the grubs. The latter 
live in the interior of their host, eating the fat, but leaving 
untouched the vital organs, till at last, when growth has 
been completed by the parasites, they either form cocoons 
inside its body, or else burrow out through the skin, 
to become pupæ in some concealment, where, though 
helpless, they may remain safe. True parasites of this- 
latter sort belong, with rare exceptions, to the Diptera or 
ee a ae ey EEN 
