University of Michigan 



PLATE I 



Figure I. Wing photograph of Agriogomphus sylvicola Selys, one of 

 the two females on which the descriptions of both genus and species 

 were based. Through the kindness of Mons. Severin, who made the 

 photograph at the request of Dr. Ris, the following data are available : 

 The two specimens of this species are under a green label written by de 

 Selys "Agriogomphus sylvicola Bates." The specimen photographed 

 has a small white label "St. Paula" in an unknown hand, and a larger 

 white label "Agriogomphus sylvicola Bates, female" in de Selys' hand. 



PLATE It 



Figure 2. Male accessory genitalia of Archacogomphus hamatus, 

 Fundacion, Colombia, January lo, 191 7. 



The striking characteristics of the penis are its relatively weak 

 chitinization, and its great complexity, especially of the second seg- 

 ment. The ventral process or spur of this segment is. in Archaeo- 

 gomphus hamatus, like a broad shovel, being fully as wide as the wide 

 second segment. Its attachment to the second segment is in the shape 

 of a low capital T, the cross of the T being basal. The apex and the 

 three borders of the broad spur are well chitinized but the enclosed 

 parts are progressively less chitinized toward the point of attachment, 

 so only the extremities of the T-shaped base are well chitinized, the 

 foot of the stem of the T (the apical extremity of the attachment) be- 

 ing most strongly chitinized. On either side of the stem of the T and 

 almost parallel to it (slightly divergent) there is a thin expanded mem- 

 brane, like a curtain, triangular in shape, attached to the second seg- 

 ment, with the distal edge free. 



The distal median portion of the second segment is not chitinized, 

 being a membranous expansion between the chitinized basal and lateral 

 areas. From this membranous floor on either side rises a thin blade- 

 like chitinized process or spine. The segment is terminated on the 

 same surface by two thin curved chitinized flaps, joined and more or 

 less margined with the usual thin membrane. 



The dorsal and ventral basal surfaces of the third segment have 

 each a similar thin membranous extension, which in each case' has a 

 free distal edge. 



