xlvi 



and which has been termed "Arrenotoky" by Leuckart (the 

 variation in which female progeny only are produced in many 

 Cynipidcs having been termed "Thelytoky" by Siebold). This 

 remarkable fact was observed nearly fifty years ago by R. Thom 

 (Loudon, Gard. Mag., vii., p. 196), who, however, being loth to 

 believe in anything so extraordinary as " lucina sine concubitu," 

 thought that there must have been a connection between the male 

 and female caterpillars, especially as he had often noticed these 

 caterpillars with their tails curled around each other. The 

 females of Nematus ventricosus lays its eggs on the surface of the 

 leaf, and not in a groove formed by its saws, which are almost 

 destitute of teeth, and which leads Dr. Riley to regard them as an 

 instance of defunctionation of special parts, in which the teeth of 

 the saw of the promordial sawfly have become degraded or reduced 

 to almost nothing ! 



A case of parthenogenesis in a spider [Segestria perjida, Walck.) 

 is recorded by Holmgren in the ' Organo de la Soc. Zool. Argen- 

 tina,' tome ii., Entrega iv. (Cordova, 1877). 



The wonderful modifications which occur in the development 

 of many of the species of Aphides, especially those of the j^oung 

 Phylloxera, have continued to occupy the attention of M. Lichten- 

 stein, who has published a resume of his observations in the 

 'Annals' of the Entomological Society of Belgium (vol. xix.), in 

 which we find stated the anomalous fact that in certain groups. 

 Phylloxera and Rhizaphis, some of the individuals are found in a 

 partially winged state which is only transitory — " ne servant que 

 de vehicule a la forme parfaite sexuee, un veritable cocon volant, 

 si je puis m'exprimer ainsi." The small wingless Aphides pro- 

 duced from these winged " cocons volants" are destitute of 

 rostrum, but furnished with organs of generation, " et s'accouplent 

 des leur naissance " ! The following short table is given of this 

 curious group, which, from a fancied analogy with the development 

 of a flower, are termed 



Anthogenetic Homoptera. 



Insects characterized by a special pupiferous form, serving as an envelope 

 from which the sexual specimens escape.* 



* This " cocon volant" seems to me to be identical with the pseudo-nymph state 

 of the Ephemeridce. 



