302 STREPSIPTERA 



the larval growth considerable sexual differentiation occurs (Fig. 

 155, C, D) ; details are, however, wanting, and there exists but 

 little information as to the later stages. Hence it is scarcely 

 a matter for surprise that authorities differ as to which is the 

 head and which the anal extremity of the adult female. Von 

 Siebold apparently entertained no doubt as to the part of the 

 female that is extruded being the anterior extremity ; indeed he 

 called it a cephalo thorax. Supposing this view to be correct, we are 

 met by the extraordinary facts that the female extrudes the head 

 for copulatory purposes, that the genital orifice is placed thereon, 

 and that the young escape by it. Meinert l contends that the 

 so-called cephalothorax of the adult is the anal extremity, and 

 that fertilisation and the escape of the young are effected by the 

 natural passages, the anterior parts of the body being affected by 

 a complete degeneration. Nassonoff, in controversion of Meinert, 

 has recently pointed out that the " cephalothorax " of the young 

 is shown by the nervous system to be the anterior extremity. It 

 still remains, however, to be shewn that the " cephalothorax " of 

 the adult female corresponds with that of the young, and we shall 

 not be surprised if Meinert prove to be correct. The internal 

 anatomy and the processes of oogenesis appear to be of a very unusual 

 character, but their details are far from clear. Brandt has given 

 some particulars as to the nervous system ; though he does not 

 say whether taken from the male or female, we may presume it to 

 be from the former ; there is a supra -oesophageal ganglion, and 

 near it a large mass which consists of two parts, the anterior repre- 

 senting the sub-oesophageal and the first thoracic ganglia, while 

 the posterior represents two of the thoracic and most of the 

 abdominal ganglia of other Insects ; at the posterior extremity, 

 connected with the other ganglia by a very long and slender 

 commissure, there is another abdominal ganglion. 2 



It is a matter of great difficulty to procure material for the 

 prosecution of this study ; the fact that the instars to be observed 

 exist only in the interior of a few Hymenopterous larvae, which 

 in the case of the bee, Andrena, are concealed under ground ; and 

 in the case of the wasps, Polistes, placed in cells in a nest of 

 wasps, adds greatly to the difficulty. It is therefore of interest 

 to know that Strepsiptera occur in Insects with incomplete 



1 Eut. Meddel. v. 1896. p. 148, and Ov. Danske Selsk. 1896, p. 67. 

 2 Horae Soc. cut. liuss. xiv. 1879, p. 14. 



