591.16 316 [May 



III 



A New Method of Asexual Reproduction in 

 Hymenopterous Insects^ 



Asexual reproduction may manifest itself among insects at 

 i\ different stages in their life-history. Sometimes it is the 

 larvae which reproduce new larvae by budding in the interior of 

 their body (paedogenesis) ; at other times it is the adults which 

 give birth to new individuals which develop in the ovaries of the 

 parents (parthenogenesis). We have just discovered in the parasitic 

 Hymeuoptera a new mode of reproduction which completes this 

 series of phenomena, of which it constitutes to some extent the first 

 step ; in Encyrtus fuscicollis which we have observed, it is in fact at 

 the very beginning of the life-history, in the egg itself, that the dis- 

 sociation of the body is produced, and it is at the expense of a single 

 egg that we have just seen a very large number of embryos arise, 

 perhaps more than one hundred, and all destined to become perfect 

 insects which will Ije for the most part of one and the same sex. 



Mr E. Bugnion had already observed that the caterpillars of the 

 Hyponomeuta of the spindle-tree may, during June, contain chains 

 of very curious parasitic embryos. These chains, of which only a 

 single example is usually found in each caterpillar host, are formed 

 on an average of from fifty to a hundred individuals arranged one 

 after the other, enclosed in a granular mass similar to a vitellus and 

 surrounded by a common long epithelial tube which is closed at both 

 ends and floats in the lymph of the caterpillar by the side of the 

 digestive tube. Bugnion followed the development of these embryos 

 and observed that each of them gave birth to an Encyrtus fuscicollis. 

 How and where does the Encyrtus accomplish its oviposition ? What 

 especially are the origin and significance of the common epithelial 

 tube enveloping the chain of embrj^os ? These are questions well 

 adapted to excite the curiosity of the naturalist. Mr Bugnion 

 thought that the Encyrtus, hatched in the spring, hibernated or 

 exhibited a second generation with an unknown animal as its host ; 

 he assumed that, in any case, it must lay its eggs in packets during 

 the month of May inside the caterpillar of the Hyponomeuta ; as to 

 the epithelial tube, it arose, according to him, from the enveloping 



^ Translated from a reprint from the Comptes Reiulus of the Paris Academy of 

 Sciences, Feb. 28, 1898, communicated by the Author. 



