Microscopical Society of Victoria. 91 
As these dykes do not, so far as I can ascertain, occur out of 
the granite area, it is, I think, most probable that they are, in 
fact, adherents to the granitic rocks. These latter have locally 
either the character of an ortlioclase and hornblende, or of a 
plagioclase and hornblende, rock, and it is these two classes of 
rocks which the dykes at Granite Creek and Bulgoback Creek 
respectively represent. The granitic rocks in these two varieties 
belong to the ampliibole granites and the quartz diorites.* 
According to these views, the dykes would belong to the same 
great age as the granites, but at its later period. This age is not, 
I think, older than Upper Silurian, and not younger than Upper 
Devonian. 
Uoio the Lerp Crystal Palace is Built. 
By W. H. Wooster. 
[With Plate.] 
[Read 29th July, 1880.] 
Many of our Eucalypts are infested with scale insects, 
commonly called Lerp, but which belong to the family Psyllida ?, 
of the order Uoinoptera. These insects in the larval state protect 
themselves from the sun and their enemies by building over 
themselves little tents, or rather crystal palaces, composed of a 
gummy and sugary secretion, which is exuded in a semi-liquid 
state from a tube at the hinder end of the body. I have taken 
at least three species, one of which makes its scale almost exactly 
like a minute oyster shell, slightly convex, the rings of 
enlargement being added to the edge in such a way as to leave 
the starting point of the scale still at one edge, as at the hinge 
of the oyster shell. This species leaves its scale plain; nothing 
is added on the outside for ornament or defence. A second 
species constructs its house like a basin, the increase being added 
round the edge equally, thus keeping the starting point in the 
centre. This kind of scale is covered all over with curved silky 
hairs or loops, often longer than its diameter, which are so 
* The samples examined of the variety characterised by ortlioclase felspar 
showed also strong affinities with the granitites, magnesia mica being 
present. This rock may, therefore, be even regarded as standing between 
amphibole granite and granitite. 
