Mr. R. Shelford's Studies of the Blattidae. 255 



favour the view that they constitute a somewhat primitive 

 group, for Australia is universally regarded as the last 

 refuge of animal forms that have disappeared from the 

 less isolated quarters of the globe. But I do not think 

 that the Blattiaae as a whole can be considered as other 

 than the most highly evolved group of cockroaches, since 

 the structure of the genital valves in the female sex is 

 -certainly a peculiar modification and not a primitive 

 character, whilst the male genitalia are more complex 

 than in many other subfamilies. Whether the BlaUa- 

 group is more primitive than the Poly zoster ia-^vovi^, is open 

 to argument, but I am inclined to think that it is not. 



Structurally the Pohjzosteriae offer valuable diagnostic 

 characters, especially in the male sex, so that the separation 

 of the species is not attended with the difficulties that con- 

 front one when dealing with such homogeneous genera as 

 Epilampra, Blabcra, Gyna, etc. ; but the allocation of the 

 females of some genera to their respective males is not 

 easy and the descriptioos of new species from females 

 alone ought to be avoided in future. 



Bionomically these insects are very interesting: some 

 are brightly coloured, e. g. Euzosteria mitchellii, and the 

 shining black species of Platyzosteria must also be very 

 conspicuous. Many of the species have a disgusting odour, 

 and one species of Cosmozosteria identified by Mr. J. J. 

 Walker as C. lateralis extrudes from the apex of the 

 abdomen when irritated a red vesicle and emits an odour 

 so pungent that Mr. Walker was deterred from capturing 

 specimens. Mr. Froggatt tells me that all the species 

 expose themselves freely and are frequently found basking 

 on the tops of fence-posts. The egg-capsules of a few 

 species are known, and are typically Blattine in form. 



KEY TO GENERA. 



1. Ocelli usually absent. Tegminal rudi- 

 ments absent. Abdominal tergites with 

 well-marked stigmatic dots. Supra- 

 anal lamina ( $ ) more or less bilobate. 

 Cerci blunt and flattened, generally 

 not extending beyond the supra-anal 

 lamina. 



2. Tibial spines in two rows Polyzosteria, Burm. 



2'. Tibial spines in three rows .... Euzosteria, nov. 



