Dr. Filippi on the Generation of an Hymenopterous Insect. 463 



here set forth ; the first parasite never continued to live and be- 

 come developed on its own account. It is besides so small that 

 it could not be perforated by the ovipositor of the Pteromalian 

 female; and the larva of the latter is developed in its interior in 

 a very different manner from the other Ichneumonidce which 

 arise from an ovum. The first parasite is, in truth, only the 

 generator of the Pteromalian larva; it is, to use Steenstrup's 

 phrase, a nurse. How has it been formed and introduced into 

 the ovum of the Rhynchites ? How do the spring broods of Fte- 

 romalidce proceed ? How do they live ? When do they deposit 

 the product of their new copulation ? for from the state of their 

 sexual organs we must suppose that they produce a new genera- 

 tion within the year. All this is to be discovered. However it 

 may be, this insect presents the only example known at present 

 in the class, of a true generation by nurses. The propagation of 

 the Aphides appears to me to be a very different affair. In fact, 

 the viviparous individuals of these insects are true females and 

 have well-developed sexual organs : their young proceed from ova 

 which are developed in the ordinary manner, as M. Ley dig has 

 recently demonstrated (Siebold and Kolliker's Zeitschrift fiir 

 Wissenschaftliche Zoologie, vol. ii.). The course of events here, is 

 just as if the viviparous females were fecundated by the influence 

 of the copulation of their immediate or remote progenitors. This 

 example of Parthenogenesis (according to the elegant expression 

 of Mr. Owen) takes place sometimes exceptionally in other spe- 

 cies of insects. I shall confine myself here to mentioning the 

 singular case, which was related to me recently by a celebrated 

 English entomologist, Mr. John Curtis, in his passage through 

 Turin ; of an isolated chrysalis of Bombijx polyphemus which he 

 had received from America, and from which a female proceeded, 

 all of w^hose ova produced young. I believe that the same 

 thing sometimes takes place in the Bombyx Mori, although 

 altogether separated from the males. But we cannot speak 

 of ova in the interior of the nurse of my Pteromalian, any more 

 than in those of the Distomata or in the larvje of Mediisidae and 

 Ophiurid(B. 



Perhaps these observations may throw some light upon the 

 complicated history of other parasitic insects, especially of 

 Xenos and of Meloe, which has been made known to us by 

 the beautiful investigations of Siebold and Newport. 



Analogy leads us to believe that the active larvae of these in- 

 sects, provided with three pair of legs, do not become transformed 

 into inert vermiform larvse, but produce them : there w^ould then 

 be in these parasites also a nursing generation. 



[The Translator feels bound to remark, first, that in his 

 belief M. Leydig's observations do not lead to the conclusion 

 that the viviparous Aphides are true females ; and secondly, that 



