87 
that only the underside is seen. Then they have the remarkable 
habit of moving the hindwings alternately up and down, whereby 
the threadlike prolongations are kept in a constant movement, 
looking perfectly like antennæ. The conspicuously coloured spot at 
the base of the pseudo-antennæ perfectly suggests an eye — and 
thus the impression is produced that this end is the head, the real 
antennæ being held quite motionless, and the real head being 
black and quite inconspicuous. Pl. I, Figs. 1, 2, 5 and 6 represent 
forms of this simple type. A much more elaborate form is repre- 
sented by the species Thecla phaleros L. and related forms (Pl. I, 
Figs. 3, 7—8). Here a lobe of the hindwing is bent outwards, 
being differently coloured from the rest of the wing. This gives 
the most wonderful likeness to a real, broad head. Furthermore 
the smaller processes suggest the palps; although they are placed 
above the antennæ, this is not noticed in the living animal, where 
these appendages are in a constant movement. It is true, this is 
not like a. butterfly-head, but a more generalized insect head; the 
resemblance to such an insect head is truly astonishing, and the 
result is that anybody would involuntarily take the tail end to be 
the head. And it can hardly be supposed that a bird or a lizard 
or any other enemy of the butterfly (Mantis?) would be suspicious 
on account of the fact that the ,head" looks remarkable for a 
butterfly or that the palps are in a wrong position. 
So vivid is the impression, in the more perfect species, that 
although I knew it all perfectly well and had observed it many 
times, I had always the involuntary impression that the tail end 
was the head, and, of course, persons with no special knowledge 
of insects would invariably take this to be the head. Once I was 
accompanied on an excursion by a clever boy, who had a fancy 
for collecting butterflies. I pointed out to him one of the black 
Striped Thecla's, asking him, where the head was. He at once 
Pointed to the tail end, and on my saying it was in the other end, 
he repeated that it was there, in the tail end. As I then pointed 
Out to him the real antennæ and head, he exclaimed wondering: 
»Oh, but then it has got two heads." 
The meaning of this can, of course, only be this one, that the 
enemies of the butterfly are induced to attack this non-vital part, 
while the butterfly itself escapes with the loss only of a part of 
