markinps and attitudes of lepidopterous larvm. 323 



are almost always of a passive kind. When active 

 (flagella) they seem to be directed against the attacks of 

 ichneumons, which produce fatal results in quite another 

 way. Nearly all the means of defence against other 

 enemies are such as tend to prevent the larva from 

 being seen or touched, rarely such as to be of any avail 

 when actually attacked. There may be various changes 

 in the mode of defence, but the object is always the 

 same, — to leave the larva untouched, a touch being 

 practically fatal. If the disguise of a twig-like Geometer 

 be seen through, in some cases the larva may drop to 

 the ground ; but, if followed, there is no further defence. 

 The larva of C. elpenor is protected by resemblance to 

 the brown or green (according to its colour) parts of its 

 food-plant. When it is discovered and attacked it 

 assumes the terrifying attitude, but, if this fail to 

 terrify, it possesses no other means of protection. So 

 also the unpleasant taste or smell are powerless for 

 those foes which attack the larvae notwithstanding such 

 protection, and the " warning colours " of distasteful 

 larvffi have been acquired to prevent experimental or 

 inadvertent *' tasting " on the part of enemies (which 

 would, of course, be fatal owing to the larval con- 

 struction). And of all the various modes of protection, 

 by far the commonest is that of resemblance to sur- 

 rounding objects, a means for rendering the larva 

 practically invisible. It seems probable that the 

 extremely perfect and very various means of defence 

 are related to the unusual delicacy which results from 

 larval organisation. 



Explanation of Plate VII. 



Fig. 1, X 4 diam. — The larva of SpJdnx ligiistri jnst after hatch- 

 ing, extended in walking. There are no markings, the colour is 

 yellowish, the head greenish. There are two rows of hairs on the 

 back, two hairs in each row upon most of the segments. There is 

 another row of hairs upon each side slightly above the spiracles 

 (with the same arrangement of hairs). The hairs are scattered 

 thinly and irregularly upon the head and posterior to the 7th 

 abdominal segment. The caudal horn is seen to be immensely 

 long, and distinctly bifid at the tip. Its colour is black, but the 

 upper half is greenish, because the black surface is rather trans- 



