424 ON THE NEW GENUS AUSTROGYN ACANTHA. 



made it impossible to obtain any Aeschnidce worth mentioning. 

 A week after I left, however, my friend Mr. Olive found this 

 species by no means uncommon there, and he has since then 

 forwarded me six males and six females. These, in spite of con- 

 siderable damage in transit by post, afford me sufficient material 

 for the present paper. Doubtless de Selys felt, when describing 

 the female, that its smaller size and very different markings and 

 colouration might warrant the formation of a new genus to con- 

 tain it; at least the name heterogena irresistibly suggests the 

 impression it made upon his mind. But it was not de Selys' way 

 to propose a new genus for a unique female, which possessed all 

 the more essential characters of the genus Gynacantha as denned 

 by Rambur. Later on Forster,* in instituting the new genus 

 Karschia for the reception of his species Gynacantha cornuta and 

 G. angulata, of which the females alone were known, seems to have 

 set a precedent which it would not be wise to follow. It is at 

 least evident that the characteristics of his genus are incomplete, 

 and must necessarily suffer alterations and additions when the 

 males of his species are discovered. It is also evident that when he 

 speculates as to the probable number of cells in the anal triangle of 

 the hindwing of the unknown male, he is not dealing with facts at 

 all, and such speculations should be rigidly kept out of his generic 

 definition. With the male of G heterogena before me, I can go 

 so far as to say that no odonatologist could possibly have pre- 

 dicted the extraordinary form of its anal angle, either by examina- 

 tion of the corresponding cells of the female, or by drawing on 

 his imagination. Even with the added knowledge of the group 

 that this remarkable insect has given me, 1 am not at all prepared 

 to say what the males of Karschia cornuta and angulata will be 

 like. They might possess either a two-, three-, or four-celled anal 

 triangle, and it may be either sharply angulated, as in the true 

 species of Gynacantha, or of the peculiar rounded form found in 



* Odonaten aus Neu-Guinea, von F. Forster in Bretten, ii.; Termesze- 

 trajzi Fuzetek, xxiii. Kot. 1900 (" Beraerkungen zur Gattung Gynacantha 

 Bamb."). 



