142 



This view being questioned by Handlirsch (1903) led 

 Heymons to a fuller examination of the whole subject, in which 

 (1904) he re-afhrmed his previous belief, although he substituted 

 the name " cercoids " for " processus caudales." While his 

 statement of observed fact was accepted by Handlirsch (1904), 

 a difference of interpretation remained as to whether the " cer- 

 coids " or " superior appendages " of the adults represent newly- 

 acquired parts not homologous with Orthoj)terous cerci (Hey- 

 mons), or whether they are but reformations of true cerci 

 (Handlirsch). For myself I favour the former idea. 



Mating Positions and Structures. 



The consideration of the morphology of the terminal abdominal 

 appendages of the adult Odonata naturally leads to that of 

 their function, and while it has long been known that these 

 parts of the males grasp the females in the act of mating, it was 

 not until our own period that the difíerences in the employ- 

 ment of these parts in the two suborders of the Odonata were 

 pointed out. Previous statements were to the eñect that the 

 male's appendages grasped the " neck," that is, the prothorax, 

 of the female, but in 1899, and again in 1906, Williamson called 

 attention to the fact that in the Anisoptera it is the head,' in 

 the Z3^goptera the prothorax of the female that is seized. It 

 will be seen, therefore, that the diñerence in the part of the 

 female grasped coincides with a difference in the morphology of 

 the "inferior appendage "ci the male which grasps. 



TiLLYARD (1909) has found that in the Australian Petalura 

 gigantea both head and mesothorax of the female are enclosed 

 between the male's appendages. The fact is interesting for a 

 number of reasons. The Petalurinie are Anisoptera, and have 

 been considered by some writers (Calvert 1893, Ris 1896, van 

 DER Weele 1906) as, of all their suborder, nearest to the Zygop- 

 tera. This copulatory position of P. gigantea gives some sug- 

 gestion as to the divergence in this position between Zygoptera 

 and Anisoptera. Petalura, however, is a true Anisopter in that 



^ There is, however, a recent discordant statement — that of Till yard 

 (1910), who asserts that the male Synthemis eustalacta clasps the female's 

 prothorax. 



