126 
DoBsoN_, 071 Laap, or Lerp. 
They are of a waxy consistence^ and tasteless. The lower 
part is a thin film adhering to the surface of the leaf; the 
upper is much thicker^ and covers the insect enclosed as in 
a bivalve shell. Overlapping each other like the scales of a 
fish^ the upper valves form two rows down the sides of the 
leaf. The perfect insect (fig. 7, nat. size) is about one 
half larger than the cone-forming Psylla, the head and pro- 
thorax are of a bright yellow^ the remaining segments of 
the thorax are dark brown^ the abdomen a yellow green, 
and the elytra yellow,, with two elongated dark brown spots at 
each tip. 
When my attention was first directed to this subject, more 
than four months ago, I found, besides the common white 
lerp and its occupant, a larger and difi*erently coloured lerp, 
with its peculiar Psylla, surpassing in beauty and structural 
development the species already described. The eggs of this 
third species are of a deep black-red colour, sometimes dis- 
posed in groups, sometimes isolated, and occasionally on the 
same leaf as those of the first kind. The colour of the larva 
is a reddish brown. The first shell-like coverings are little 
transparent, and in many parts quite opaque and dark brown. 
Its form is remarkably like to that of one valve of a cockle- 
shell. (Fig. 5.) The apex or hinge is always well attached 
to the leaf. As the insect grows, the digestive or secretory 
functions seem to be more perfectly performed, and the 
material of the covering become of a rich canary-yellow colour, 
and very translucent. The shell of yellow lerp varies in 
diameter from one third to one half of an inch. 
The strong threads all rise from near the point of attach- 
ment, which is at the cleft of the heart-shaped base, and 
arching over meet the leaf. 
Around this fixed point the leaf is always more or less 
dried up and discoloured. A thick tuft of curling hairs rises 
from the neighbourhood of the apex. The finer stride, which 
are disposed parallel to the surface of the leaf, and line the 
roof, are quite distinct and separate from each other. Around 
the base is a broad flat band of an open reticulated texture. 
A white filmy carpet, composed of extremely fine threads 
crossing in all directions, completes the interior of this 
beautiful structure. The pupa and perfect insect are twice as 
large as those which fabricate the white lerp. 
The head and thorax are more highly coloured, and the 
abdomen of a warmer green. (Fig. 6.) 
The elytra and wings are diaphanous, but the wing-cases 
of the j)upa, and the elegant symmetiical nervures of the 
elytra of the perfect insect, are of a bright scarlet colour. 
