AN ENCYCLOPADIA 
OF HORTICULTURE. 185 
Insects—continued. 
Two-winged Flies (Tachina and allied genera), or to certain 
divisions of the Hymenoptera. In this latter order, some 
groups, with very numerous kinds in each, are entirely, or 
Fic. 293. ICHNEUMON PLy. 
almost entirely, confined to parasitism (Ichneumons—see 
Fig. 293—and Chalcidide), and many species in the other 
groups of the order are also parasites. In fact, it may 
almost be said that there are few Insects which are 
not preyed on by one or more (and frequently by many) 
of these minute parasites. It is hardly in our power to do 
anything directly to increase the numbers of these allies; 
but it is well to be able to recognise their general 
appearance, and to refrain from killing them. 
In many cases, however, we must not trust to the 
efforts of birds and Insects to limit the numbers of 
our Insect foes. When their attacks are severe, it is 
necessary to remove or to destroy them more rapidly than 
can be done by natural agencies; and, though the methods 
employed must be varied to suit the special circumstances 
that call for them, yet the same methods are largely ap- 
plicable for the destruction of many kinds of Insects. A 
few of the more generally useful may be mentioned here. 
Tobacco smoke is very fatal to many of the hurtful 
Insects, where these attack plants under cover, e.g., in 
greenhouses. It is especially efficacious against Aphides. 
Either strong coarse tobacco, or the paper in which it 
has been wrapped, is burned in the place to be freed 
from the foe; the doors are all kept closed during the 
operation, and for some time afterwards. Infusions of 
tobacco, of Hellebore, or of other insecticides, are some- 
times prepared, and are scattered over the plants by 
means of a watering pot or syringe. These applica- 
tions are usually very fatal to larve feeding on such 
parts of plants as allow of the solution being properly 
applied to them, and they do not injure the host. Scale, 
and other Insects that lie closely adherent to leaves or 
branches, are seldom much affected by tobacco smoke, 
and they are best removed by washing the parts with 
water, or with solutions of soft soap or of poisonous sub- 
stances; and the efficacy of the applications is increased 
by using a brush to put them on with. Several kinds 
of injurious larve are in the habit of living in groups, 
in or under webs. These are easily cleared away 
with the webs; and the whole should be destroyed, by 
burning or otherwise. Larve living in the interior of 
branches, or in galls, cannot be reached without remov- 
ing the injured structures; and this is also usually 
the case with root-feeders. When a plant is withering 
without any apparent cause, the removal of the earth 
from its root will, at times, disclose the hidden larva that 
has been feeding there. Sometimes, also, larve feed at 
night on the leaves, and during the day hide themselves 
in the earth. Hence, the depredators can be detected 
only at night, by the use of a lantern. Many Insect 
larvee roll up a leaf, or spin together two or three leaves, 
so as to form a protection for themselves against all 
means of destruction save hand - picking ; but, fortu- 
nately, such larva are seldom fatal in their attacks ; 
though, frequently, the plants become very unsightly 
under them. ‘Trees and shrubs are attacked in this 
way more often than are herbaceous plants. - A severe 
shaking will often cause a large number of the larvæ to 
drop from their tubes, and to hang suspended in the air 
by silken threads till the danger is past, when they | 
remount by their threads. If a sheet is spread below 
Vol. I. 
Insects—continued. 
the tree, they may be shaken on to it, and then readily 
gathered to be destroyed. The mere shaking of the 
plant is not enough. Many larvee (e.g., those of Gooseberry 
Sawflies, of Winter Moth, &c., fall to the ground when 
full fed, there to burrow in order to form cocoons, and 
to become pupæ, within a very little distance of the 
surface of the ground. Soot, gas-lime, and other nauseous . 
materials are often spread on the soil around the stems 
of trees and shrubs, to prevent the larva from burrow- 
ing in the immediate vicinity of the plants, and to de- 
stroy them by the poisonous properties of the substances. 
The pupw may be greatly lessened in number by paring 
off, and burning an inch or two of the surface soil in the 
autumn or winter. Opening the soil with a hoe or a rake 
is also useful, as it destroys some pupæ at once, and ex- 
poses others to the chance of being eaten by birds, and 
to unfavourable conditions during the winter., The 
females of some of the more hurtful Insects are wing- 
less, or have wings so small as to be of little or no 
Fig. 7 294); they must, 
— — to under the names of the various in- 
The —— has been divided into certain great — 
groups, called “ orders,” by means of characters taken mostly — 
from the structure of the mouth and of the wings, and 
from the kind of metamorphosis they pass through in 
their growth. These orders are well distinguished from 
one another, and there is usually not much difficulty in 
determining the group to which any Insect belongs. 
Some orders are of far greater importance to gardeners 
than are others; and to them the following remarks are 
‘confined. These orders are as follows: 
These have the mouth formed 
Coleoptera, or Beetles. 
2 B 
