136 NEW ZEALAND NATURE-STUDY BOOK 
Aphids and Scale Insects. These are small insect- 
forms which are found in immense numbers on certain kinds 
of plants causing in some cases great devastation. The best 
known amongst the Aphids perhaps are the Blue Blight 
Fig. 93.—Black Aphis.—(2) Apterous viviparous female. (3) Pupa. (4) Winged 
viviparous female. (5) Winged male. (6) Oviparous female. All magnified. 
which often attacks cabbages ; the Black Aphis so harmful 
to fruit trees; and the Phylloxera so injurious to vines. 
Methods of Preventing Spread of the Insects. 
The insect itself is such a formidable pest that every possible 
