1, 1904. J 
Supplement to the "Tropical AgricuUunst." 
573 
Some of them — indeed, the majority — undergo 
during their development well-marked transfor- 
mation or stages: 1st, the egg; 'iiid, the larvie or 
c:\terpiUar; 3rd, the pupa or chrysalis; 4tli, the 
adult or imago stage. Moths and butteiflie?, 
amongst others, beloiig to tliis class. In two or, 
may be, three periods of their transformation they 
take no food, and are fixtures; during these periods 
they do no actual harm. Thus, butterflies and 
molhs are inert in the egg as well as the pupa 
stages ; and some of them, such as the codlin moth, 
for instance, do not feed. Vet it is during tliese 
periods of rest and transformation that it is often 
easier to attack them. Tliese insects undergo 
what is called comjilete tramformation, in contra- 
distinction of others which undergo incomplete 
transformation. This second class, such as grass- 
hoppers and locusts, have eggs which, in hatching, 
give forth young insects which only differ from 
the full-grown ones in size and in possessing no 
wings. Instead of changing from larva to pupa, 
they proceed, by a series of moulting or casting 
off their skin, to the mature stage, and become 
imago. During these successive moulting3 they 
are known as " nymphs.'' 
Again, some insects lay eggs and are "oviparous"; 
■while others bring forth^their young alive, and are 
"viviparous." The majority of them, however, 
proceed from the egg, whetiier that egg is deposited 
cemented to the plant by means of a viscous 
secretion or whetiier they give birth to young ones. 
In the latter case the female insect generally carries 
the egg internally until the hatching period arrives. 
So much for the life history af insects, considered 
broadly. A number of varieties depart from t];e 
pattern laid down in several minor details which 
cannot be touched upon in this paper, although a 
clear understanding of these particularities is of 
great assistance in combating pests. They often 
consilute the weak point of the armour it is meant 
to penetrate, and serve as a guide in directing the 
attack against them. 
Almost as important as an understanding of the 
life history of pests is a knowledge of the manner 
they attack plants when taking their food. 
In that respect noxious pests may be considered, 
irrespective of their classification, names, shape, 
or colour, into two general types : bitiny and 
chewing insects and sap-sucking insects. The for- 
mer are often leaf-eaters or bark-uibblers, or, again, 
■wood and fruit borers. They are provided with 
jaws by which they can gnaw the surface of the 
food plant, and chew it. 
The latter feed on the juices of the inner tissues 
of the host-plant. They are armed width a pointed 
tube-like beak, which they thrust into the tissues 
of their host-plant, and suck out the sap. 
Of Ihe biting or food-che'wing insects, 
some are : — 
(1) lloot-eaters ; such as the white worm of the 
cockchafter, the larvM of the cicadtc. 
(2) Others, bark-nibblers ; as certain kinds of 
beetles and of weevils. 
(3) Some are leaf-eaters ; as slugs, caterpillars, 
saw-flies' larva, the carpenter bee, 
^4) Others injure the bud, the blossom, or the 
fruit ; as the strawberry weevil, the codliu 
{noth, 
Of the sucking insects, in a like manner 
some are ; — ■ 
(1) Eoot-sucking insects ; as the woolly apliis 
and phylloxera of the vine. 
(2) Others, ordinary bark-sucking insects ; ns 
the mealy bugs. 
(3) Some leaf and bud or fruit sucking insects; 
as the rose and the orange aphis, the red 
and other scales, and plant bugs. 
When fighting against biting insects, their food 
plant is best coated with substances which will 
net as internal poisons ; whereas, when directing 
the at^ck against sap-sucking insects, the 
treatmfTit must be such as hurts and kills by direct 
contact ; they are external irritants, and act from 
the outside either closing the breathing pores or 
killing by irritation of the skin. 
To the first category belong the various combi- 
nations of arsenic, and chief amongst them "Paris 
green," a chemical combination of arsenic and 
copper. When unadulterated it contains 5.5 to 60 
per cent, of arsenic. It is almost insoluble in 
water. It is applied either — 1st, dry in a state 
of impalpable powder, mixed in the proportion of 
1 oz. of Paris green with 2 lb. flour, slaked lime, 
road-dust, or ashes ; 2iid, or in a liquid mixture in 
the proportion of 1 oz, in 10 gallons of water. 
It should not be used in conjunction ■with any acid 
substance which would dissolve the arsenic it 
contains and make it caustic, but, on the contrary, 
it is always a good plan to add to it a handful of 
lime, which has the property of turning insoluble 
aiiy trace of caustic arsenic it contains, Being a 
heavy substance, it quickly settles to the bottom 
of the pumping tackle, and requires agitating. 
Other combinations of arsenic, such as London 
purple and arsenic and soda solution, are also used, 
but genuine and unadulterated Paris green is the 
best. A little glue or flour paste may be added to 
cause it to adhere better, especially to plants with 
glossy leaves. 
Hellebore, unlike the arsenites, which are 
mineral poisons, is a vegetable poison, and is less 
dangerous. It is a powder made of the roots of the 
white hellebore, and kills both by contact and by 
being eaten. Very effective when fresh, it loses 
its strength by standing. In doses 1 oz, to 3 
g illons of water it is much used against the pear 
slug and leaf-eating worms. 
Piirethrum, or insectibane, is also a poison, and 
is effective when fresh, but loses strength when 
exposed to the air. It is made from the powdered 
flowers of plants of the genus Pt/rethrim. That 
light-brown powder is dusted over the plants or 
sprayed, in the proportion of pyrethrum one table- 
spoonful, boiling water two gallons. It kills by 
contact, and should be applied as long as the 
insects presist. Burnt over hot coals in the 
conservatories and greenhouses, it rids plants of 
aphis and other insect pests. Pyrethrum are easily 
cultivated, make pretty borders, and a supply of 
fresh flowers could, without trouble, be raised in 
every garden. 
Kerosene, in the form of an emulsion with 
soapsuds, or mechanically mixed with water in the 
form of a misty spray, in the proportion of one 
of kerosene and four of water, will kill nearly all 
insects, and not injure the foliage, 
