Vol. xxvii] ENTOMOLOGICAL NEWS. ght) 
On Certain Acanthagrions, Including Three New 
Species (Odonata). 
By E. B. WiitiaMson, 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 
Acanthagrion 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, 
