338 COSTA RICAN EPIGOMPHUS (oDONATa) 



bordered on each side with brown; three to six dark brown, with a mid-dor- 

 sal, longitudinal, pale line, or on three and four only, five and six with a small 

 basal spot; three with a yellowish stripe each side from base almost to apex; 

 four to six with a yellowish spot or stripe each side occupying the anterior 

 fourth to seven-ninths on four, fourth to five-sixths (but then less distinct) 

 on five, fourth to third on six; seven yellowish in its anterior three-fifths 

 to four-fifths, except for a transverse browTi fine each side at one-third of the 

 segment's length, the remainder brown; eight to ten dark brown with indis- 

 tinct yellowish markings on each side inferiorly for the entire length of these 

 segments. 



9 . Vulvar lamina .84 to .91 mm. long, reaching to .4 to .65 of the length 

 of the lateral margin of segment nine, bilobed in the distal .5 to .62 of its 

 own length, interval between the lobes triangular. 



Epigomphus armatus 



Epigomphus armatus Ris, Archiv f. Naturgesch., 82 Jahrg., Abteil A. 9, Heft, 

 pp. 146, 147, 148, figs. 90 (thor. pattern), 91-93 (apps. cf ), 1918. 

 The following notes are based on the material Usted antea, page 326: 

 9 . Pale color on the dorsal surface of the frons widely separated as two 

 spots, right and left. 



Metepimeron apparently with no dark stripe near its ventral margin 

 (none shown in Dr. Ris' figure 90). 



Abdominal segment two faded, apparently ^ith a broad, basal, dorsal, 

 yellomsh area contracted on the posterior half of the segment to a narrow, 

 longituchnal stripe, stripe bordered each side with brown; three to six with a 

 mid-dorsal, longitudinal, yellow Une apparently confluent at base with yellow 

 which extends the entire length of the sides but is crossed by a transverse 

 blackish fine at one-third the length of each segment; seven yellowish, only 

 a similar transverse stripe and the hindmost sixth of the segment blackish 

 eight to ten blackish, yellowish on the sides inferiorly for most of the length 

 of eight and indistinctly on nine. 



9 . Vulvar lamina .77 to .84 mm. long, reacliing to .57 to .59 of the length 

 of the lateral margin of segment nine, bilobed in the distal .45 to .5 of its 

 length, lobes more nearly parallel than in the other species, but this may 

 be due to individual or mechanical conditions of the spe-jimens. 



Mutual Mating Adaptations 



Soon after making my collection of Odonata in Costa Rica I 

 noticed the modifications which the specimens of Epigomphus 

 presented and made this note for my future guidance: "A com- 

 parative study of the shapes of the apps. d" and the vertex, 

 occiput and rear of head 9 ought to give some interesting sexual 

 co-adaptations." In 1910, Dr. F. Ris interpreted '' the pres- 

 ence of certain scars on the compound eyes of females of Anax 



24Kopulationsmarken bei Libellcn. l)euts(!he Entom. National-Biblio- 

 thek, I, pp. 70-80. 



