348 COSTA RICAN EPIGOMPHUS (oDONATA) 



E. subohtusus referred to postea under that species, but in none 

 of the seven females of subsimilis is there any suggestion of tu- 

 bercles replacing them. 



The vertex and occiput of the male are similar to those of the female but 

 the rear of his head is not differentiated into pit, ridge and groove. The 

 vertices of the two sexes have been compared anlca, page 334. 



Epigomphus subobtusus (PI. XIV, figs. 15 to 17.) 



In this species the adaptations of the head of the female to the 

 appendages of the male seem to be less marked than in any of the 

 other species here treated. Two females from Costa Rica and 

 three from Guatemala (as mentioned antea, pages 336 and 337) are 

 before me. I find on the right side of the rear of the head of the 

 female from south of Aguacaliente (fig. 17) what I take for a scar 

 with some dried exudations attached; it is very distinct, is 

 elongated, subvertical, its position corresponds to a level of about 

 three-fifths the distance from the mesal eye margin of the dorsal 

 surface of the head to the lateral surface of the eye, and its inferior 

 end is on the same horizontal level as the mesad-directed angle 

 of the posterior eye margin. It appears to correspond to the pit 

 (p) rather than to the postgenal cicatrix of other species. No 

 scar is observable on the left side of the head, not even in the 

 "geringe Andeutung elner Struktur von der Ai't des annatus-9 ; 

 eine flache Vertiefung, neben der Medialwarts eine Wolbung 

 steht, die aber in der Dorsalansicht nicht sichtbar'" ist," des- 

 cribed by Dr. Ris. No similar scars are visible on the heads of 

 the other four females, nor do I find any scars on the dorsal sur- 

 face of the head in any of the five specimens. 



By analogy we should expect, of course, that the superior 

 appendages of the male are applied against the rear of the head 

 of the female, when pairing, and that the scar {p) above described 

 marks the contact made by the lateral apical angle (p', fig. 15) 

 of the right appendage. 



In both the description and figure of the female occiput in the Biologia vol- 

 ume I have indicated the presence of a pair of well-marked superior tubercles. 

 Dr. Ris does not mention these and I find the following conditions to exist 

 with respef^t to them in the present material. In the female from south of 

 AguacaUente, C. R., both of these tubercles are well developed and simihir 

 to the Biologia figure (figs. 16, 17, dot). In the female from below Juan Vinas 



8iln the five females before me the "Wolbung" is visible in what I should 

 call a dorsal view of the head; cf. fig. 16. 



