DoBSON, on Laap, or Lerp. 
125 
ocelli separated by the furrow. This duality of organ accords 
well with analogy;, and disposes me to believe that what has 
been hitherto considered a third central ocellus is really a 
combination of two minute ocelli^ whose proximity and 
oblique position render them incapable of separation by our 
microscopes. 
The wings are much longer than the body^ and nearly 
colourless. The elytra are longer than the wings^ almost of 
the same consistence^ and defiexed. The abdomen is of a 
rich emerald green^ and is terminated by two pointed project- 
ing pieces^ which play an important part in depositing the 
eggs and constructing the roof. The feet are furnished with 
two hooks_, and a small membranous bladder. These vesicular 
appendages_, as well as the antennse_, are continually in motion. 
The insect seems to prefer locomotion by running and leaping 
to that by flight. The male is somewhat smaller than the 
female^, but presents no prominent difference in other respects. 
The description given by Dr. Anderson in the ^ Edinburgh 
New Philosophical JournaP for July^ 1849^ of the form and 
structure of the small white cones^ is sufficiently minute and 
accurate. The tuft of hairs seen on most specimens consists 
of portions of the thick central thread which have failed to 
retain their hold on the surface of the leaf. If Dr. Anderson 
is correct in stating that the saccharine taste of lerp is con- 
fined entirely to these external hairs_, there must exist a 
remarkable difference between the usual excrementitious 
matter of which these hairs are composed^ and that secreted 
and expelled from between the abdominal rings^ &c. In 
insects which subsist on vegetable juices^, the salivary vessels 
are developed in an extraordinary degree ; and whether the 
fine silky filaments exude from the salivary glands^ as in the 
caterpillar, or are elaborated by a special secretory apparatus_, 
it is quite conceivable that their nature may be very different 
fr'om that of the excrementitious matter which has been sub- 
jected to the action of the various organs composing the 
intestinal canal. The ants are extremely fond of lerp ; and 
the beautifully marked spider whose dwelling is a gum-leaf 
folded and laced together by white threads, has generally one 
or two tenanted cones and a large ball of fluid lerp within its 
abode. 
I have recently met with another species of Psylla located 
on the red- curled leaves at the extremities of fresh young 
shoots, and protected by a different kind of lerp. The edges 
of the leaf are turned over so as nearly to meet ; and within 
each of the two grooves thus formed is a series of white 
opaque shells of an elongated oval shape. (Fig. 3.) 
