156 Mr. Poulton's notes in 1885 upon 



keeping one of these larvre, and ho was quite convinced 

 that the true significance of these niavkings upon the 

 third thoracic segment was that wliich has been described 

 above. These two eye-hke marks differ from the others 

 in that they only possess significance in the terrifying 

 attitude, being quite unrecognisable as eyes in any other 

 position. This must certainly add to the effect of the 

 suddenly assumed protective attitude, when, in addition to 

 the changed contour of the larva and the prominence given 

 to the large eye- spots, with equal suddenness new terrify- 

 ing marks seem, as it were, to spring into existence. 



G. The tereifying attitude of the larva of Dicra- 

 NURA viNULA. — I think there is no doubt that the anterior 

 view of this larva possesses exactly the same significance 

 as that of the Chm'ocmnjxi larvae, but in the former case 

 the effect is less elaborately produced, and is not in- 

 tensified by the accessory and important eye-like marks 

 on the back. The large head of the larva of D. vinula 

 is withdrawn during rest into the first thoracic segment, 

 so that the latter forms a broad margin round the head, 

 which is coloured differently from the rest of the larval 

 surface, being bright red. Thus a very large flat face 

 appears to extend to the outer edge of the red margin, 

 and superiorly upon this margin, in an appropriate 

 position, are two large intensely black spots, which 

 produce all the effect of eyes. The duct of the gland 

 which secretes the acid defensive fluid opens in a hori- 

 zontal slit on the red margin below the true head, and is 

 thus placed in such a position that its contents are 

 ejected with an anterior direction. Disturbance causes 

 the larva to withdraw its head still further and to inflate 

 the red margin, especially in the region of the gland 

 duct, and at the same time the head is always turned in 

 the direction of the disturbance. Thus the fluid is 

 thrown towards the cause of the irritation, and the 

 terrifying appearance of the larval full face is also 

 brought to bear upon it. These movements of the head 

 take place before and after the ejection of the fluid, and 

 in those cases when it is not ejected at all. Such 

 terrifying attitudes and markings as these of course 

 apply, and probably only apply, to vertebrate enemies 

 (bird's), and the effects produced approximate somewhat 

 to an intensely exaggerated caricature of a sort of 



