154 Mr. Poulton's 7iotes in 1885 upon 



5. A NEW POINT IN THE TERRIFYING ATTITUDE OF THE 



LARVA OF Ch.erocampa elpenor. — During the past 

 summer (1885) I obtained two nearly fully-grown larvae 

 of C. elpenor, upon which the following observations 

 were made. Both were found near Oxford, one from the 

 Isis and the other from the Cherwell. I found the latter 

 in a bed of Epilohium hirsutuin (the usual food-plant), in 

 which a few plants of Lythrmn purpureum were growing. 

 My wife pointed out to me that, although the larva was 

 clinging to a stem of an Epilohium, it was actually 

 engaged in eating a leaf of the Ljjilirum. I afterwards 

 offered it both food-plants, and found that the Lf/tJtrum 

 was eaten quite as readily as the Epilohium. I have not 

 seen any instance recorded of the larva eating this food- 

 plant, and I have certainly never noticed it before. 



The ontogeny of this larva has l)een very carefully 

 and completely worked out by Weismann (see English 

 translation by Prof. R. Meldola). Weismann describes 

 the origin of the large eye-like spots on the first and 

 second abdominal segments, and their use in the later 

 stages as terrifying markings. It is especially note- 

 worthy that the terrifying appearance due to these 

 markings would be effective against an enemy ap- 

 proaching from the side or from above, but would 

 produce very little, if any, effect upon an enemy ad- 

 vancing from the front. At the same time it seemed to 

 me that the larva is more sensitive to very slight tactile 

 impressions on its head than elsewhere, and most 

 readily takes up the terrifying attitude on such a 

 stimulus. In other words, the larva readily meets the 

 approach of an enemy in front by taking up a position 

 which defends it from enemies coming from other 

 directions, but which (as far as the well-known eye-spots 

 arc concerned) is comparatively unavailing for the actual 

 necessity of the case. However, on looking at the larva 

 from the front, when it assumed the terrifying attitude, 

 I saw at once that it is well protected from this point of 

 view by another pair of eye-like marks, which appear 

 in the defensive attitude only, upon the third thoracic 

 segment. This new eye-spot is produced by modifications 

 in the remains of the light subdorsal line, which persists 

 upon the thoracic segments, and is bordered above and 

 below with a dark margin. Weismann alludes to this 

 line, and, in tlic case of G. porcellus (p. 187), says of the 



