22 INSECTS NOXIOUS TO AGKICULTUEE. 



liable to attack, some of the Diaspidinse next, and the Coccidinse 

 least of all. Mytilaspis pomorum, so hurtful to apple-trees, does 

 not seem to be attacked. leery a 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 astelia 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 mast have a 

 very considerable effect in preventing the increase of Coccididse, 

 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 camellia, Lecanium hesperidum, 

 Lecanium olea, Lecanium hemisphcericum, Pulvinaria camellicola , 

 and Icerya purchasi. Here reference is made not so much 

 to insects which render plants unsightly as to those which 

 seriously injiire its growth : many others, such as Fiorinia 

 astelice or Ctenochiton viridis are ugly enough, but have not 

 been destructive. Of the injurious species above named none, 

 apparently, are troubled in this country by parasitic insects up 

 to the present time, at least to any appreciable extent. 



A sketch of Ctenochiton enclosing a parasitic pupa, and of 

 the perfect fly, will be found in Plate xxiii. In a work like this 

 the generic and specific characters of these parasites need not be 

 given : thev 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 Eriochiton 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 ; KermapMs pini is equally, if not more, destructive- 



