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peculiar structure. They vary in length from about "18 to 

 •08 of a millimetre ; they are very finely tapered towards the 

 end by which they are attached, and the outer end, which is 

 much thicker, is furnished with three or four large sharp 

 barbs, similar projections of gradually decreasing size being 

 profusely arranged along the whole length of the hair, or 

 spicule, as it may be termed. These spicule hairs, which in 

 the case of the processionary caterpillars have been described 

 by Judeich and Nitsche, occur in enormous numbers, and I 

 believe that to them is mainly due the inflammation which 

 ensues from contact with the larva. 



Now in the female moth, P. similis, microscopic examination 

 of the hairs in the anal tuft shows that there are present three 

 lxxx] 



kinds of hairs. First, long thick hairs, having a smooth and 

 innocuous surface. These are most numerous on the peri- 

 pheral portion of the tuft, in fact all the hairs here seem to be 

 of the smooth kind, but they occur also in considerable 

 numbers throughout. 



Secondly, there are great masses of very fine hairs which 

 for a portion only of their length are covered with irregular 

 sharp jagged processes. A bundle of these hairs, when highly 

 magnified, presents much the appearance of a tangle of 

 brambles. These hairs are quite different from the large 

 hairs of the larva. Also it is to be noted that it is the basal 

 end of the hair which is spiny, so that when the moth has 

 made a tuft over its eggs the spiny part will be uppermost, 

 and so in the position to be first touched by an enemy. 

 Thirdly, and this seems the most remarkable fact, there are 

 amongst the two kinds of hairs already described, great 

 numbers of little spicule hairs apparently precisely similar to 

 those found in such profusion on the larva. One is at first 

 tempted to suppose that these may in fact be derived from 

 the larval skin in the cocoon, but unless the moth in emerging 

 deliberately thrusts aside the pupal skin and brushes that of 

 the larva with its tail, it seems difficult to understand how it 

 can acquire them from any external source, and it therefore 

 seems probable that the moth can grow these spicules just as 

 the larva does. I am taking measures to find out how these 



