326 Dr. Frederick A. Dixey on ' 



little doubt that its use has reference only to the resting 

 position. 



The aspect suggested is rather that of several forms of 

 Heliconms in general than that of any one in particular; 

 the most definite relation, however, is with the group of 

 which Heliconius cychio and H. galantlms are examples, a 

 group characterised by the presence on both surfaces, but 

 especiallybeneath, of a gooddeal of light yellowoften paling 

 further to white. When the undersides of Pieris locusta 

 and one of these Heliconii, say H. cydno (which inhabits 

 the same part of the neotropical region), are compared 

 together, both insects being in the resting position, we 

 find not indeed an exact resemblance, but a general 

 similarity which, judging from other instances, we may 

 consider as probably sufficient to suggest the possession of 

 like qualities. In both there occurs on the forewing a 

 certain amount of white ground colour; on one side 

 bounded by a dark tip, and on the other more or less 

 limited by the dark area of the hiudwing ; which latter 

 is traversed by a bright yellow streak, and beset about 

 the base with red or chestnut patches. The elements of 

 the pattern in both insects are the same, and their 

 general relation to one another much alike, though the 

 pale marginal band on the hindwing that occurs in 

 this species of Heliconius is not found in the Pierine. 

 A further point of interest is the manner in which 

 the partial breaking up of the white colour is effected 

 in the Heliconius and the Pieris respectively. There 

 is, I think, liitle doubt that the dark marks on 

 the costa of the hindwing in P. locusta represent 

 in a general way the dark discoidal spot and a 

 portion of the inner dark area of the forewing in the 

 Heliconius. The bright yellow line of the hindwing will 

 be seen in each case to terminate in relation with a dark 

 patch ; but in the first instance (that of the Pieris) this 

 belongs to the same wing; and in the second instance 

 (that of the Heliconius) it is contributed to by both 

 wings. This seems to exemplify a principle repeatedly 

 met with in mimicry ; viz., that exact homology is dis- 

 regarded, and the whole exposed surface of the insect is 

 taken as it were as a canvas on which the mimetic 

 picture is painted with a free hand. The relation of this 

 particular group of Heliconius with the Pierines is 

 remarkable, and deserves more detailed treatment ; here 



