346 COSTA RICAN EPIGOMPHUS (odONATa) 



A comparison of the male appendages and head of the female 

 make it likely that, in pairing, the lateral apical angle (p') of his 

 superior appendages is received into the deep, post-genal pit 

 (p),the mesal apical angle {pgc') of the same causes the post- 

 cephalic cicatrix (pcjc), the outer division (fig. 8, soc') of the apex 

 of each branch of his inferior appendage sometimes producing 

 the superior ocular cicatrix (soc) the acute superior basal tooth 

 of each branch of the same appendage entering the superior 

 pit (dof) of her occiput. I had thought at first that the inner 

 division of the apex of each branch of his inferior appendage 

 might be applied against the posterior surface of the elevation of 

 her lateral ocellus, but the distance between the superior ocular 

 cicatrix and the shght depression on the hind surface of this 

 elevation of the same side of the head, in the two females which 

 show these cicatrices, is too great to allow one to suppose that 

 these two positions could be occupied by the divisions of the apex 

 at the same time. Whether the cicatrices are made in the at- 

 tempt to adjust the inner division of the apex to the ocellar 

 elevations, or whether pairing may occur without this adjustment 

 being made, must be determined by actual observations of the 

 insects when mating. It should, however, be pointed out that 

 the superior occipital pits of the female can not receive the su- 

 perior basal teeth of the branches of the male's inferior appen- 

 dage when the inner divisions of the apices of those branches are 

 applied against her ocellar elevations, as the distance again is 

 too great. 



In the vertex of the male each lateral ocellus hes on the summit of an ele- 

 vation which summit is much nearer (.14 mm.) to the mesal margin of the 

 adjoining compound eye than to the mid-dorsal line of the head (.56 mm.); 

 meso-caudad to each ocellus, but lower on the elevation, is a ridge or "wall" 

 (Ris) whose crest is rounded and which in dorsal view shows as a curve with 

 its convexity cephalad, the curves behind the two ocelli meeting on the mid- 

 dorsal line; this ridge at no point is as high as the ocellus, as is the case in E. 

 subobtusus. The elevations of the right and left ocelh are separated by a 

 depression, which in posterior view is not deep as one-half of the height of 

 either elevation. 



In the vertex of the female the ridge or wall is lacking or indistinct and the 

 depression between the two ocellar elevations is deeper, being more than 

 one-half as deep as the height of either elevation when viewed from beliind. 

 The lateral ocelli are situated with respect to the compound eyes and the mid- 

 dorsal line as in the male. 



