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 
Fieliconius in general than that of any one in particular ; 
the most definite relation, however, is with the group of 
which Heliconius cydno and H. galanthus are examples, a 
group characterised by the presence on both surfaces, but 
especially beneath, of a good deal 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 
hike 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 hindwing ; 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, little doubt that the dark marks on 
the costa of the hindwing in P. locusta represent 
i a general way the dark discoidal spot and a 
portion of the inner dark area of the forewing in the 
Heliconius. he 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. ‘'his 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 Heliconiws with the Pierines is 
remarkable, and deserves more detailed treatment ; here 
