1919.] 
New Zealand Institute Science Congress. 
269 
The Status of Entomology in the Economy of the Dominion, by 
David Miller, Government Entomologist. 
The part played by insects in the economy of a country is a feature of 
agriculture too frequently overlooked, although, fortunately, legislation in 
New Zealand compels the control of several noxious forms. However, there 
are vet many other species which are responsible for a considerable annual 
loss to the producer, and if such inroads are allowed to occur without 
utilizing the most rigid methods of control the development of the country 
must consequently suffer — -a subject worthy of serious consideration, particu¬ 
larly at the present time, when every measure possible should be adopted to 
ensure the conservation of our resources. 
The extreme abundance of insects as compared with other forms of 
animal-life may be illustrated by spreading a newspaper upon the ground 
and shaking any overhanging vegetation into it, or by sweeping an insect- 
net through grass or the foliage of shrubs, when the number and variety 
of insects collected will be surprising. This is better understood when we 
realize that insects are numerically superior to any other group of animals, 
insect species comprising, indeed, about 80 per cent, of the animal kingdom 
(see figure). Fortunately, however, those species with noxious inclinations 
are not only in the minority, but also are suppressed, more or less, by an 
extensive section of their fellows, which carries on a relentless warfare upon 
them. Corresponding with the numerical inferiority of the injurious species 
to those preying upon them, the former are considerably more fertile than 
the latter, but the fertility varies according to the severity of the attacking 
species. Owing to the factors controlling the equilibrium, under normal 
conditions only a comparative few out of the excessive numbers of young 
produced by a noxious insect reach maturity; but as soon as a favour¬ 
able chance occurs there results a sudden increase of the pest, often with 
disastrous results. 
Insects become noxious only when detrimental to man’s economy ; they 
are never so in a free state, since there they aid in preserving an equili¬ 
brium amongst the vegetation, &c., just as the parasitic and predaceous 
insects are a means towards repressing any undue increase of their fellows. 
However, both the former and the latter differ in their economic appli¬ 
cation. Those species forsaking their natural diet for the products of 
man at once become useless and a danger to his economy, whereas the 
natural habits of the predaceous and parasitic forms can still be utilized 
either as a main factor or as auxiliaries in the suppression of their noxious 
brethren. 
In New Zealand, as in most young countries, we find that our noxious 
insects originate from two sources : (1) A few of the indigenous species 
have forsaken their natural habitat and, by attacking man’s products, have 
become injurious ; (2) several of the injurious forms have been accidentally 
introduced from other countries, and these are the most numerous and 
their depredations are the most serious. The indigenous noxious forms, 
although rapidly increasing at times under favourable conditions produced 
by cultivation, are still exposed, more or less, to the controlling influence 
of certain indigenous factors ; but the exotic forms, being liberated in a 
land free from the forces suppressing them in their original homes, more 
readily become established and abnormally prolific under the new condi¬ 
tions. The establishment of an exotic insect pest to a dangerous extent 
does not in all cases follow immediately upon its introduction. Such an 
insect may never become destructive in its new home, and frequently it 
