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to understand the method by which. an Insect feeds, 
whether it be in the larval or adult condition. Almost all 
remedial measures have to be based upon this factor. We 
can recognise three methods by which Insects feed: (1) 
By means of the biting action of their jaws. (2) By means 
of sucking, and in this case the mouth organs are modified 
to form a suctorial apparatus. (3) By means of a com- 
bination of both of these methods. 
Various chemical substances are used for destroying 
Insects and are known as Insecticides. Biting Insects are 
mainly destroyed by poisoning their food, while sucking 
Insects can usually only be destroyed by using contact 
insecticides—those which kill by means of surface contact. 
This method is adopted for the simple reason that we 
cannot poison the food when it consists of the internal 
juices of plants, as is the case with sucking Insects. When 
using insecticides the grower should proceed with caution 
until experience has been acquired. Also contact insecti- 
cides are liable to injure the foliage under certain con- 
ditions. Many of the insecticides that have been recom- 
mended are inefficient, while others need scientific testing 
to fully determine their value. Insecticides are artificial 
wetbeels of control, but it 1s necessary to point out that 
the utilisation of zatural methods of control should not be 
neglected. Natural methods consist in the preservation 
and increase of those organisms which are directly bene- 
ficial to man, in that they destroy the injurious forms of 
animal life. This latter method will be dealt with in a 
subsequent lecture. 
The first order of Insects that I shall deal with is the 
Ortho piera, and the only member thereof that concerns us 
is the common Earwig (Forjicula auricularia) (10). It is 
a good example of an Insect which undergoes incomplete 
metamorphosis. The adult Earwig lays its eggs in a 
group either beneath stones or in the soil. During the 
incubation period she guards the eggs until they hatch, 
exhibiting in this respect a rudimentary instance of 
parental care. The young larve are minute white 
creatures, with very slender forceps and no traces of wings. 
After they have passed through several moults rudiments 
of wings appear, and ae ye growth chiefly consists 
of an increase in the size of the Insect and the gradual 
development of the wings. No pupa or resting stage is 
passed through. The Earwig is almost exclusively noc- 
