Occasiuiial Papers of the Alitseiiin of Zuukxjy 17 



conspicuously four-sided; and infans and hauiatus differ in the 

 thoracic color pattern. 



Agriogomphus hamatiis is the smallest gomphine known ; in 

 no other gomphine is the triangle so distinctly four-sided ; and 

 it is the only dragonfly in which the male abdominal appen- 

 dages have become functionless as grasping organs, this func- 

 tion being taken over by unique modifications of the tenth 

 abdominal segment. 



Agriogomphus species 



Dcseription : Abdomen, female 24 mm. ; hind wing, female 

 20 mm. 



Female. — Similar to Imiiicitus but separated at once by the 

 form of the occiput. Thoracic dark colors brighter, a rusty 

 brown; the dark stripe on either side of the median dark area 

 joined above to that area, and, a short distance below, broadly 

 joined to the dark antehumeral stripe. Abdominal patterns ap- 

 parently the same, the dark apices of the segments possibly 

 darker, noticeable especially on 6, where the apex and the 

 base of 7 are black. Vulvar lamina similar to that of hauiatus 

 but specifically distinct, the branches slenderer, slightly longer, 

 with their outer edges more nearly parallel, meeting the pos- 

 terior edge of the base at nearly a right angle instead of in a 

 •long curve. 



Stigma black, covering two and one-half cells (two in one 

 front wing). A^enation black, wings clear, yellow tinged basal- 

 ly and anteriorly as far as the nodus. x-Antenodals in front 

 wings, 10 or 11, in hind wings, 9; postnodals in front wings, 

 5 or 6 ; in hind wings, 5. In the front wing the number of cells 

 on the anterior side of Cu^, which do not reach '^l^, is i ; and 

 in the hind wing it is i or 2 (2 or 3 in females of hauiatus). 

 In the hind wing the number of cells posterior to Cuo. which 



