SCALE-INSECTS. 17 



chance that the honeydew spray so falling will be disturbed. It 

 consequently rapidly accumulates and forms a coating on the 

 leaf where it rests. From this result two things, or, rather, the 

 same injurious effect on the plant is produced in two ways. First, 

 the honeydew itself, being, as stated, of a glutinous nature, tends 

 to stop up and choke the stomata (or, in plain English, the 

 breathing-orifices of the leaves) and so retard the growth of the 

 tree. Secondly, the honeydew, being of a saccharine nature, is 

 especially attractive to fungoid growths, and these fungi, rapidly 

 increasing, tend still more to choke the leaves and hamper the 

 proper functions of the tree. 



The second of these is the most important, for, apparently, 

 the honeydew is scarcely deposited before it becomes the recep- 

 tacle for fungus-spores, and these grow with great rapidity. As 

 a general rule, in New Zealand, these fungi appear to be mostly 

 of the same family the Physomycetes, and they are of a black 

 or very dark brown colour. From the fact above stated, that 

 the honeydew falls from the insects upon leaves beneath them, 

 the lower leaves of a plant are more covered with it than the 

 upper ones : these black fungi consequently discolour chiefly the 

 lower leaves and branches ; often the uppermost branches are 

 nearly free from them. But the effect produced on the tree is 

 not only unsightly, from the sooty blackness, but also injurious, 

 from the choking-up of the stomata both by the honeydew and 

 the fungus. As for ornamental plants, whether under glass or 

 in the open air, the black coating is quite sufficient to spoil 

 them. 



These fungi are of various species, and specimens are given 

 here in Plate xxii. : on the leaves they form usually a hard, thin, 

 black coat ; while on the twigs and stem they are of a looser 

 texture, forming masses of minute erect threads. They are not 

 confined to New Zealand, and most writers on Coccididse in 

 Europe and elsewhere mention them, though only casually. 

 They are, in fact, apparently, only the usual growths appearing 

 on any decomposing substance, such as the honeydew is. 



Gardeners and tree-growers ought to clearly understand that 

 the appearance on their plants of this black sooty covering is 

 almost always an indication of the presence of some Homo- 

 pterous insects. In New Zealand, on account of the greater 

 prevalence of Coccididse, the insects will most probably be 

 Coccids ; but by no means necessarily so, for many Aphididse, 

 2 



