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XVIII. On the Urticating Properties of Porthesia similis, 
Fuess. By Harry Evrrincuay, M.A., D.Sc., F.Z.8. 
[Read October Ist, 1913.] 
PuateE XXII. 
In a former note * I pointed out that the urticating pro- 
perties of the female of P. sumilis were due to the presence 
in the anal tuft, of barbed spicules, apparently identical in 
structure with those of the larva, and although it seemed 
probable that the moth derived its spicules from the 
cocoon, the manner in which it did so was not very obvious, 
since although there are many spicules in the cocoon the 
body of the moth would seem to be protected from contact, 
even during emergence, by the pupal skin. 
During the past summer I have had an opportunity of 
studying the subject more fully, with extremely interesting 
results. ‘1 am indebted to Prof. Poulton for many useful 
suggestions, and to Commander Walker and Mr. A. H. 
Hamm for a portion of the material for my experiments. 
The larva, though well known, seems not to have been 
examined very minutely, and it may be of interest to 
describe the structure in relation to the spicules, as revealed 
by a series of sections. 
The spicules occur on every segment except the first and 
second. The third and fourth segments have two extra 
large masses which meet dorsally. On each remaining seg- 
ment they occur on two dorsal and two dorso-lateral pro- 
jections. Plate XXII, fig. 2, shows a diagrammatic section 
of half a segment, the spicule tufts being marked S. 
The large hairs (h) arise from chitinous sockets which 
seem to occur all over the larva, though especially numerous 
on the lateral projections. These hairs are branched as 
shown in the figure. Amongst the dorso-lateral spicules 
are found white plume-like structures, one of which is shown 
at Plate XXII, fig. 2 (p). Occasionally these arise on the 
dorsal tufts also, To the unaided eye their matted branches 
* Proc. Ent. Soc. Lond., p. Ixxx, 1912. 
TRANS. ENT. SOC. LOND. 1913.—PaRT IN. (JAN.) FF 
