28 PARTHENOGENESIS IN SOME 



reproductive process just described by me in Solenobia trique- 

 trella and lichenella. 



The two species of Sac-bearers just mentioned are not however 

 the only representatives of the true Parthenogenesis ; an equally 

 striking example of the virgin reproduction of a female insect is 

 presented by Psyche Helix. Of this extremely remarkable moth 

 we are at present only certainly acquainted with the female. In 

 the caterpillar state it lives in a sac, which in its form resembles 

 a sinistral snail-shell, to which similarity the specific name given 

 by me to this Psyche also refers. 



The sac of Psyche Helix is nearly as large as a small pea 

 (generally 2 lines Rhenish in height, and the same in breadth) ; 

 it exhibits three and a half whorls (figs. 1-3), and consists of a 

 firm whitish tissue, which is thickly and firmly coated externally 

 with small particles of earth. The colour of the sac is usually 

 earthy-grey, but in certain districts blackish or reddish-brown 

 sacs occur ; this is probably in connexion with the colour of 

 the soil from which these Sac-bearers partly derive the material 

 for their sacs. Here and there also individual cases occur with 

 separate whorls (anfractibus devolutis). The uppermost and 

 narrowest half-turn is always very indistinct, and generally ap- 

 pears collapsed. At the place where the second whorl com- 

 mences there is always a lateral opening (figs. 2, 3, & 6 a), the 

 margins of which usually lie down and conceal the entrance 

 to the cavity of the whorl*. When the caterpillar has evacu- 



* Besides Psyche Helix, there are some other insects, whose larvae, as case- 

 bearers, manufacture sacs in the form of a snail-shell. In the genus Psyche 

 itself there occurs another species, the caterpillars of which, like those of 

 Psyche Helix, bear about with them a spirally-twisted sac. By the kindness 

 of Herr Zeller of Glogau and Dr. Rosenhauer of Erlangen, I possess two 

 earth -coloured, snail-like sacs with perfectly flat convolutions (figs. 15-17), 

 found in Sicily and Spain. They are nearly three times as large as the sacs 

 of Psyche Helix, and from their different form and size belong to another spe- 

 cies, to which I will give the provisional name of Psyche Planorbis. Both 

 sacs, like those of Psyche Helix, are covered with fine grains of earth and sand 

 cemented on them. Behind the uppermost and narrowest half-turn there is also 

 a lateral aperture, which is due to an interruption in the walls of the sac taking 

 place here (fig. 15 a). In the family of the Phryyanidce also, larvae occur, 

 which form a spirally-twisted domicile. The first notice of this was furnished 

 by Shuttleworth (in the Mittheilungen der naturforschenden Gesellschaft in 

 Bern, June 1843, p. 20), and as this is but little known, I will reproduce it 



