100 OCCASIONAL PAPERS. 



tail ; in 1829 Latreille called it Dicranura or fork- 

 tail, a name which it still bears, though in fact both 

 are in use. You will ask for what purpose have the 

 anal claspers undergone this curious transformation, 

 or if a Darwinian, you will want to knew what com- 

 bination of physical conditions favoured its occur- 

 rence. Well, these questions have not been answered 

 as yet, at any rate satisfactorily ; here is another 

 opportunity for any of you to make the discovery 

 by careful watching and experimenting. Out of 

 these horny cases, as they really are, the creature 

 can project tiny scarlet threads to some considerable 

 distance ; this it will always do if you disturb or 

 irritate it by touching it, or if another larva does so. 

 It has been supposed that these threads serve as a 

 kind of protection weapons of defence against 

 small enemies, particularly the ichneumon flies to 

 which we shall presently refer. And when the 

 peculiar attitude of the larva is assumed, the head 

 thrown up and back, and the tail recurved so as to 

 throw the whole body into a concave form, these 

 threads can sweep over it all, so that there is con- 

 siderable probability in the conjecture. But, on the 

 other hand, these larvae do not seem to be more 

 exempt than others from the successful attacks of 

 these and other parasites. So the question remains 

 undecided. 



The caterpillar has, however, another mode of 

 defence by way of attack, namely, the ejection of a 

 fluid acrid in its nature, and causing a slight smart- 

 ing on the skin, but probably more powerful when di- 

 rected against minute enemies. This power is possess- 

 ed by some beetles among other creatures ; Iremem- 



