242 COMMON BRITISH INSECTS. 



The fourth segment is produced into a large and 

 pointed hump, and from the ninth segment the body 

 tapers to the end. Here are developed two rough 

 horn-like projections, from each of which can be 

 protruded a horny pink filament, which seems to be 

 employed as a weapon. It has been suggested that 

 these appendages are used for the purpose of driving 

 away ichneumon-flies when they settle on the body 

 in the hope of depositing their eggs. Whether this 

 theory be correct or not is undetermined, but the 

 caterpillar certainly does protrude them when irritated. 

 The larva has another weapon, if it may be so called. 

 Below the head there is a transverse slit about the 

 sixth of an inch in length. When the creature is 

 alarmed or angered, from this aperture is ejected a 

 fluid of an acrid character, which may probably have 

 some injurious or deterrent effect upon the enemies of 

 the Puss Moth larva. 



The colour of this caterpillar is singularly beau- 

 tiful leaf-green on the sides and whitish above, with 

 some stripes of purple brown. Between these two 

 colours a white stripe runs from the side of the head 

 to the tip of the hump, and then passes to the base of 

 the double tail. The stripes are so arranged that 

 when the larva is viewed from above, they appear 

 something like the capital letter X- In some speci- 

 mens, though not in all, there is a large purple patch 

 on the eighth segment. 



This larva feeds both on the willow and poplar, 

 and, being very hardy, is easily reared throughout its 

 changes. When full-fed, which takes place about the 

 end of May, it leaves its food, crawls down the trunk 

 of the tree, and creeps into some convenient crevice of 



