282 The Irish Naturalist. 



that the caterpillar of Odo7itopera, which is also sometimes 

 dark, and sometimes greenish (as the specimen photographed) 

 is sensitive in the same way as the insects on which Prof. 

 Poulton experimented. 



Besides its protective resemblance, this caterpillar of 

 Odo7itopera has another point of considerable interest. It was 

 mentioned above that in looping caterpillars the three front 

 pairs of claspers are wanting. This is generally the case, but, 

 like most statements about natural objects, some qualification 

 is required. In a few loopers one or two of these pairs of 

 claspers are present in a greatly reduced or vestigial condition, 

 and in Odontopera the foremost pair alone is entirely wanting. 

 In fig. I one of these vestigial claspers can be clearly seen 

 just beyond the end of the twig to which the insect clings. 

 These reduced organs tell us that this race of caterpillars were 

 not loopers always, but that their ancestral moths had cater- 

 pillars with the full number of claspers. It is possible that 

 the twig-imitating habit of the group may have helped the 

 disappearance of the front claspers, which would rather spoil 

 the imitative effect. 



It will be remarked that the term '' protective resemblance'* 

 has been used for the likeness of ^lis caterpillar to a twig. 

 The term " mimicry," sometimes employed in this connection, 

 should be reserved for another kind of imitative appearance, 

 the resemblance of an animal to another animal, which belongs 

 to a different group, and which is protected by some noxious 

 or distasteful character. The likenesses of certain moths and 

 two-winged flies to the stinging bees and wasps are examples 

 of mimicry. 



For many years the facts of protective resemblance and 

 mimicry among insects, have been received without doubt as 

 testimonies to the action of natural selection. Irately, however, 

 it has been questioned whether the advantages derived from 

 these likenesses are so great as had been supposed. The 

 accepted interpretation of the phenomena is so natural 

 and beautiful, that it will not be abandoned until a better is 

 forthcoming, which many of us think will never be. But no 

 accepted theories should blind the eyes of the naturalist to 

 the reception of new light. Observations in the field and 

 careful experiments can alone determine what amount of 

 benefit these creatures derive from their deceptive appearance. 



