Nor, indeed, can it be said that in New Zealand itself the attacks of scale-insects out-of-doors are harmless. Apple orchards throughout the country bear evidence to the contrary: lemon-groves can be seen about Auckland where, instead of the thousands of fruit formerly grown, a few stunted lemons are all that the withered trees afford; and nobody can glance round the plantations at Nelson or Napier without recognizing the devastating powers of a scale-insect (_Icerya_). The opinion that Coccids are not likely to do much harm in the open air is therefore scarcely tenable, and it will be of use to inquire what remedies can be provided against them. There is a point, however, to be noted at the outset, and it is, that in reality there is not, as far as is yet known, any _certain_ remedy against scale-insects. Not that ingenuity and experiment have not succeeded in inventing plans and substances quite efficient in killing the insects when applied to them. It is easy enough to kill an insect when you can get at it, in most cases; but the problem in this instance is not only to kill individual insects, but to do more. What is wanted is to get rid of whole communities of them, and, at the same time, to prevent their eggs from hatching and a new brood coming forth. Many of those who profess to know all about destroying "scale"--especially if they belong to that class which prides itself upon being "practical men"--being generally quite ignorant of the habits and life-history of the insects, are satisfied when they have tried some rule-of-thumb plan which seems to kill most of the adult insects, not dreaming that they have left the eggs unharmed and ready to send forth a fresh swarm at hatching-time. There is another obstacle which often prevents success in eradicating "scale." This is the difficulty of making sure of the effects of any remedy. A plan which has answered well in one place will fail in another, and this, not only as regards different countries, but even in the same district for neighbouring gardens, or even for neighbouring trees in the same garden. Tree-growers must be prepared to find the very same remedy which has cleared their neighbours' trees fail for their own; and in this country the author has seen, in one and the same orchard, some trees quite cleared, while on others, treated in exactly a similar manner, the "scale" was scarcely injured. It is from want of knowledge of this and the like points that persons who have tried various remedies recommended to them have complained of failure, and condemned both the remedy and their adviser, whilst really neither was in fault.