1 Junn, 1898. ] QUEENSLAND AGRICULTURAL JOURNAL. 497 
ringed. ‘These scales are usually of different sizes according as they are 
mature or not, and placed side by side or even densely overlapping. Hach of 
them is the outward manifestation of an individual <Aspidiotus perniciosus 
insect. ‘These appearances are shown on Plate XL., figs. 4 and 5, giving 
the results of higher magnification than that attainable by use of the means 
named. i 
Beneath this encrusting mass of scale insects the true bark, dull as if from 
the application of some corrosive fluid, will be found to be darker than usual, 
and, on being cut into, to have become deeply tinged with a purplish-brown 
colour. ; 
If the whole tree is similarly affected, as may happen, this condition 
obtains on every limb and branch. Some of the latter will have already died, 
others may emit only weak tufts of leaves from here and there. The plant 
will in a very manifest manner have ceased. to thrive. 
Partial Infestation —When trees are but partially infested attention may 
be claimed in the first instance by certain peculiar features presented by the 
young wood, the leaves, or even the fruit ; and these are what may be exhibited 
by nursery stock in a more or less pronounced degree. On the young wood— 
and especially is this the case with the peach and its allies—and on the bark of 
the sprouts or suckers, darkened purplish-coloured depressions may be observed © 
that on being closely scrutinised will be found to be occupied by little nests of 
scales.* Or circular, well-defined purple spots may be noticeable —perhaps one 
or two only—along the course of the young stems. ‘he centres of these may 
be occupied by individual scale insects ; but this may not happen, as the spots, 
persist long after the latter have attained the limit of their vitality and fallen 
away. Similarly coloured and conditioned small blotches may be noticeable on 
the leaf-stalks and leaves themselves; and in the case of the latter usually’ 
where the side veins join the central one. In the fruit of different ages, the 
purple rounded spots may be plainly discerned, especially in the region of the 
eye. (Plate XLL, Fig. 12.) 
It must be borne in mind, however, that the occurrence of these purple 
spots, with or without scales in their centres, is not absolutely characteristic, as 
has been repeatedly affirmed.¢ Glossy (é.2., waxy) skinned apples may not. 
exhibit it; so also may be the case with the wood of certain varieties of trees, 
especially when the insect has settled down late in autumn; or where the bark 
has already commenced to harden as in wounds, but generally these spots are 
nevertheless a good indication of the presence of San José Scale on the stems. 
The insect, however, if present and not revealing itself by these surface 
discolourations, will in the first instance be detected—and here the employment. 
of a lens is essential—on the older wood, in the roughened surfaces occurring 
where branches arise or bifureate, in old wounds left by pruning, &c., in skin 
abrasions, and fissures, behind buds, in the cores of apples, beneath their 
sepals, or even within the calyx tube. 
THE INSECT. 
The female insects (Plate XLI., figs. 1 and 2), that occur greatly in 
excess of the males, and which often are alone remarked, have their scales 
nearly circular in outline and flatly convex, though somewhat pyramidal. The 
apex is nearly quite central, and is boss or nipple-like. It is usually surrounded’ 
by a low circular ring (erateriform). In colour it is of various shades of grey, 
with a central area (Fig. 1a; exuvie or cast-off skins) varying from yellow to 
black. In size they may have a diameter of 2 mm. (about 7 inch), but rarely 
exceed, when massed together, half that dimension. Exceptionally, however, 
when the insect occurs isolated in young wood, as shown on Plate XLL,, fig. 5, 
as it appears when highly magnified, it may attain nearly g-inch in diameter. 
* Asa pronounced illustration of this:—‘‘ Peach trees when attacked by this scale have the 
branches quite ribbed with distinct hollows in the bar, but sometimes swollen and flattened on 
the sides, so that even the tissue of the wood seems to have been altered.” (Froggatt, /.c.) 
+ A similar purple discolouration immediately surrounding the scale is also sometimes pro- 
duced by Aspidiotus rossi, Maskell. ‘This is especially noticeable when this insect occurs upon 
the apple, the fruit of which plant is quite conspicuously marked should it be present thereon. 
