Occasional Papers oj the Museum of Zoology 



II 



Cacus, are representative of the series. In the slight concavity 

 of the distal side of the triangles the Hagenius series is suggested; 

 in the dissimilar subtriangles of fore and hind wings and the dense 

 venation the Progomphus series is suggested, but the triangle of 

 the front wing tends to be longer, nearer the shape of the triangle 

 of the hind wings, in the Diastatomma series; it is unique by the 

 presence of a strongly developed sector of Rs and a usually less 

 well-developed sector of M4. Of the twenty-seven species in the 

 six genera in this series, six belong in the genus Gomphidia and 

 sixteen in Ictinus. Cacus of the Neotropical Region, with one 

 species, alone occurs in the New World; Lindenia with a single 

 species is Palaearctic; the remainder are Ethiopian and Oriental. 



The foregoing diagram indicates the relationships of the six 

 series as I understand them. From the vertical line of primitive 

 and simple winged forms the Diastatomma line branched off and 

 became by addition a densely veined type. From some dense- 

 veined member of this line a branch developed which by reduction 

 resulted in the Hagenius and Zonophora series. It is possible these 

 two series should be shown arising independently from the Diasta- 

 tomma line. The Progomphus series is another lateral branch 

 from the vertical line, developing another type of dense-veined 

 forms. From some dense- veined member of the Epigomphus 

 series a branch appeared which by reduction gave rise to the Gom- 

 phus series. 



