DoBsoN, cm Laap, or Lerp. 
123 
On L.\AP, or Lerp, the Cup-like Coverings of Psyllium found 
on the Leaves of certain Eucalypti. By Thomas Dobson, 
Esq., B.A., of tlie High School, Hobart Town. Commu- 
nicated by George Busk, Esq. 
(Read April 30th, 1856.) 
The white saccharine substance called ^''lerp,^^ by the 
Aborigines, in the north-western parts of Australia Felix, 
and which has attracted the attention of chemists, under 
the impression that it is a new species of manna, originates 
with an insect of the tribe of Psyllidce, and order Hemiptera. 
According to Latreille {' Diet. Classique d' Hist. Nat.' art. 
Psylla) only six species of this genus are known, and these 
are all proper to Europe. 
The three species described in this paper are, in all proba- 
bility, new to entomologists. 
The larvae of several insects avail themselves of their 
peculiar secretions to form a rude tent-like protection from 
their enemies and the weather. Those of the Crioceres are 
concealed under an irregular mass, ha\dng the appearance of 
macerated leaves. The Cassidce, Coccida^ and Psyllida are 
hidden under a cloak of white cottony filaments flowing 
from the articulations of the body. The Psytla Eucalypti 
enjoys a more profuse supply of glutinous pabulum than its 
European congeners, and is thus enabled to construct a more 
artificial and effective dwelling. It is, perhaps, owing to the 
remarkable dryness and mildness of the winter just past that 
these insects have been obtainable in their various phases 
of transformation at all times during the last four months. 
The white conical tents of the larvse and pupae may be 
readily detected on the leaves of the lower branches of the 
stunted gum-bushes in the Government domain here; the 
groups of minute ova are not so obvious, and the perfect 
insect is seldom seen abroad. It is more often met with in 
a quiescent state, after it has cast off its pupa skin, and 
while its wings are yet moist and shrivelled up. Its exist- 
ence in the perfect state is either very ephemeral, or it 
escapes observation by its incessant restlessness, and the 
peculiar faculty of leaping, to which it owes its generic 
name. 
To the unaided eye the eggs appear like small yellow 
granules scattered in groups on either side of the leaf, and 
unprotected by covering. (PL II, fig. 1.) 
Under the microscope they are seen to consist of a 
translucent pyriform membrane inserted into the leaf by a 
pedicle, and containing an amber-coloured fluid of somewhat 
darker hue near the neck or fixed extremity. Just before 
