99, INSECTS NOXIOUS TO AGRICULTURE. 
liable to attack, some of the Diaspidine next, and the Coccidinie 
least of all. Mytilaspis pomorum, so hurtful to apple-trees, does 
not seem to be attacked. Icerya purchasi, the worst species of 
all, has not yet furnished a single parasitic fly. A few speci- 
mens of Dactylopius glaucus contain parasites ; a good many of 
Fiorinia astelie and F. stricta ; while Ctenochiton perforatus and 
C. viridis appear to be the favourite victims, as sometimes 
scarcely any specimens on a plant can be examined which do not 
contain either a larva or a pupa of a parasite. It is to be 
observed that in no case is more than one parasite to be found 
in a Coccid. 
Unfortunately, although this provision of Nature must have a 
very considerable effect in preventing the increase of Coccidide, 
it is subject to two drawbacks. In the first place, as just 
observed, some of the most injurious pests appear to be un- 
affected by it. Probably, up to the present time the worst 
plant-enemies* in New Zealand have been Mytilaspis pomorum, 
Aspidiotus coccineus, Aspidiotus camellie, Lecanium hesperidum, 
Lecanium olee, Lecanium hemisphericum, Pulvinaria camellicola, 
and Icerya purchasi. Were reference is made not so much 
to imsects which render plants unsightly as to those which 
seriously injure its growth: many others, such as Fiorinia 
astelie or Ctenochiton viridis are ugly enough, but have not 
been destructive. Of the imjurious species above named none, 
apparently, are troubled in this country by parasitic msects up 
to the present time, at least to any appreciable extent. 
A sketch of Ctenochiton enclosmg a parasitic pupa, and of 
the perfect fly, will be found in Plate xxii. In a work like this 
the generic and specific characters of these parasites need not be 
given: they do not seem to differ much from bymenopterous 
and dipterous insects of other countries. 
Another mode by which the too, rapid increase of Coccids 
is checked is by the attacks of vegetable parasites—fungoid 
growths which permeate the whole body of the insect, and soon 
Kill it. As far as experience in New Zealand extends as yet 
the genera Ctenochiton, Lecanium, and probably Hriochiton are 
the only ones so attacked. On certain plants in the forests, 
notably Hedycarya and Coprosma, circular spots may be com- 
monly found on the under side of the leaves: some dark- 
* Speaking of Coccids only; Kermaphis pini is equally, if not more, destructive. 
