PARTHENOGENESIS IN ESYCHE HELIX. 1 59 



snail-sliell, 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 affer 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 

 PsycJiidtv, 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 liead has no antcnnce. 



