Vol. XXvii] ENTOMOLOGICAL NEWS. 313 



On Certain Acanthagrions, Including Three New 



Species (Odonata). 



By E. B. WILLIAMSON, Bluffton, Indiana. 



(Plate XVII) 



This paper is a brief account of material collected in Gua- 

 temala, British Guiana and Trinidad by B. J. Rainey, L. A. 

 Williamson and myself. At Tumatumari, British Guiana, we 

 were aided by Mr. A. F. Porter and Mr. J. M. Geddes ; and in 

 Trinidad we enjoyed the frequent companionship of Mr. F. 

 W. Urich and Mr. P. L. Guppy. 



Pruinescence. It is a matter of common observation that 

 in many agrionines pruinescence appears first on the under 

 parts of the thorax. Pruinescence in certain calopterygines 

 is known to be displayed by the male and it is possible that 

 pruinescence in agrionines may serve a similar purpose. In 

 Acanthagrlon there are between the first coxae, and probably 

 also between the second coxae, bright shining black areas 

 which, in the case of the first coxae at least, are not covered 

 with pruinescence. These black areas in their white field 

 might be displayed by the male fluttering over the female. 

 However the female is about as definitely marked as the male 

 and the theory of sexual display seems rather improbable un- 

 less the female uses the same parts to advertise her sexual ma- 

 turity. I have not examined species in other genera to see 

 how common this type of ventral coloration is. It may also 

 be noticed in this connection that the lower posterior angle of 

 the thorax is tipped with black and there is a more or less 

 definite dark longitudinal mid-ventral line on the first ab- 

 dominal segment. These various marks produce a definite 

 and uniform ventral color pattern, the most plausible value of 

 which would seem to have to do with the relation of the sexes. 



The Penis. In his study of the penis of Zygoptera Mr. 

 Kennedy has given systematic odonatology a new and valuable 

 tool. Specimens from Trinidad appeared, when judged by 

 conventional characters, to be scarcely distinct from gracile. 

 However, there were enough differences to excite suspicion, 

 and when specimens were given to Mr. Kennedy for study, 



