342 COSTA RICAN EPIGOMPHUS (oDONATA) 



probably received into two shallow depressions (dot') of his ap- 

 pendage which lie immediately distad and sUghtly mesad of his 

 forwardly-curved spines, the latter, therefore, apparently lying 

 just laterad of the occipital tubercles w^ien pairing, perhaps in 

 the parocular grooves. 



The extent to which the head of the female of this species has 

 been modified in apparent correlation with mating may be seen 

 from the following details of the structure of the head of the 

 male. 



The vertex cf the male and that of the female are dissimilar, the former 

 being hke that of quadracies male (except that the lateral ocelli are not so 

 near to the eye margins) and of both sexes of subsimilis, and lacks the con- 

 spicuous postocellar, or "vertex, tubercles" of the female. 



The occiput of the two sexes is dissimilar in that the male has shallow pits 

 dorsally where the female has tubercles and the posterior siu'face smoother 

 and less swollen. 



The rear of the head (postgenae) of the male has no transverse rounded 

 ridge and but very few traces of the subvertical impressed lines of the female. 



Epigomphus armatus (PL XV, figs. 27-30.) 



Of this species, recently described by Dr. Ris, I have two 

 females but no males. He has figured the appendages of the male 

 and I copy two of his figures; in the specimen from which figure 

 27 was made the superior appendages were apparently not as 

 widely distended as they are in the act of pairing. The apices 

 {])') of the male's superior appendages are, doubtless, received 

 into the very deep pits (PI. XV, fig. 30, p) of the rear of her head. 

 One of my females has distinct superior ocular cicatrices near the 

 angle of the mesal margin of the eyes. By analogy w'ith E. 

 verticicornis, I would expect that the apical (distal) margin of 

 the male's inferior appendage would, when pairing, be applied 

 against the posterior surfaces of the two postocellar, or vertex, 

 tubercles ("kraftige hori;iartige Fortsatze" of Dr. Ris) of the 

 female. A comparison of fig. 27 with fig. 29 shows, however, 

 that if the apices (soc') of his inferior appendage cause the cica- 

 trices, soc, the shape of the distal margin of the appendage is 

 such that it would then lie some distance away from and caudad 

 to the post-ocellar tubercles. 



In the absence of male specimens I am unable to make any 

 further suggestions. 



