272 The N.Z. Journal of Science and Technology. [July 
Factors encouraging the abnormal development of insects may be 
brought about not only by the destruction of their natural habitats, but 
also by the conservation of their normal food-supply and the artificial 
extension of conditions favourable for their welfare. This is exemplified 
by the development of the areas of native flax (Phormium tenax) and the 
resultant attack of the flax-grub (Xanthorhoe praefectata), an indigenous 
species. Formerly this insect confined itself to flax growing in dry areas, 
but on the swamps being drained, encouraging a luxuriant growth of flax 
and suitable soil conditions, this pest developed accordingly, causing exten¬ 
sive loss to the hemp industry. The approximate loss through the agency 
of the flax-grub, under normal market conditions, has been computed to 
exceed at times £120,000 per annum. 
The upsetting influence of such mutations referred to above, together 
with the establishment of exotic pests under a favourable environment, 
are responsible for the more serious aspect of insect depredations in a new 
country than in the Old World. There man’s progress in the development 
of the country has evolved so gradually over an extensive period that the 
environment has been affected in proportion to the progress until there 
now exists what may be termed a domestic equilibrium. It may be 
expected, therefore, that in New Zealand, after many generations, when 
the conditions have recovered from the inroads of man, there will evolve 
an artificial balance between him and his surroundings. 
The practical man, therefore, should bear in mind that, since he is 
tampering with nature when he opens up virgin territory for his own 
purposes, unless he can foresee and forestall any of the inevitable results 
which may be detrimental to him, he cannot expect to develop fully the 
resources under his control ; he should acquire as far as possible a practical 
knowledge of the insects affecting his products and of the best methods 
of holding them within bounds. 
At the present time our working knowledge of the destructive insects 
of New Zealand is comparatively meagre, but the subject is now being 
taken up as a special work, in order that this aspect of agriculture may 
be placed on a sound footing and that the necessary information may be 
available for practical purposes. Doubtless a reason for our ignorance of 
humanistic entomology in New Zealand lies in the fact that our entomo¬ 
logists have been, more or less, either systematists or collectors, with no 
further aim than the creation of new species, the identifications of which, 
from a practical viewpoint, are contained in an obscure maze of scientific 
nomenclature, while the humanistic relationships of these forms still lie 
beyond the horizon. To the producer this purely systematic, and con¬ 
sequently uninviting, state of our entomology is useless. 
Without the applied entomologist the systematist and the collector are 
of no practical value, but a combination of the three is an invaluable asset 
in the development of our resources. It is necessary for an insect to have 
a name and systematic position ; also, the applied entomologist, being a 
specialist in the humanistic problems of insect-life, must at times rely upon 
the systematist for identifications, especially in the more obscure groups, 
whilst invaluable information upon the geographical distribution of insects 
is the result of the collector’s labours. 
Humanistic entomology opens up an extensive field for research. Among 
the problems being taken up at present are those dealing with the ecology 
of the indigenous and exotic field-crop and orchard insects. An investi¬ 
gation of our mosquitoes and other blood-sucking forms, in relation to the 
