PARTHENOGENESIS IN PSYCHE HELIX. 159 
snail-shell, to which similarity the specific name given by me to 
this Psyche also refers.” The body of the caterpillar which makes 
this twisted case is also curved spirally, and it leaves an opening in 
the hinder whorls of the sac. The female moth lays its eggs 
inside this sac, which it occupied as caterpillar and pupa, and 
having spun down the front opening, leaves the dwelling by the 
other opening, which is large enough for its shrivelled, eggless 
body. Von Siebold proceeds: ‘“ These sac-bearers are leaf- 
miners, and push their bodies far in between the epidermic plates 
of the leaves through a round hole which they gnaw in the latter, 
and devour the green colouring-matter. During this process the 
sac remains outside, sticking with its aperture to the opening in 
the epidermis. The leaves, and even the variegated flowers, are in 
this way often completly decolourised by the sac-bearers.” ‘“ When 
these sac-bearers are full-grown—which is the case in the latter part 
of the summer—they quit the plants they have been feeding upon, 
like the other caterpillars of the genus, and seek a suitable place 
for the change into the pupa state. When they find stone walls or 
rocks in their vicinity, they creep high up on them, and spin down 
the lower aperture of their dwelling firmly. In passing through 
the process of moulting, also, these caterpillars, like all other sac- 
bearers, always spin down their habitation temporarily. The 
evolution of the moth takes place in the same year. If after some 
time we examine the spun-down sac of a Psyche helix during its 
chrysalis state, we find the pupa in the lower twist or whorl of the 
case, with its head directed upwards and its tail-end downwards, 
towards the last aperture. Between this and the tail-end of the 
pupa the shrivelled skin of the caterpillar, stripped off in its last 
change, is always fixed, so that this caterpillar, like all those of the 
Psychide, turns itself round in the sac before true pupation. In all 
the sacs of Psyche helix in the pupa state hitherto examined by 
me, of which I have had the opportunity of observing more than 
a hundred and fifty in seven years, I never found any but a 
female pupa. This is of a yellowish brown colour, and with 
very indistinct segments.” ‘The wingless and almost footless 
female moth which is evolved from this pupa also appears slightly 
curved in a spiral. Its colour is grey, with a slight brown tint on 
the back of the three thoracic segments. The head has no antenne, 
