8 University of Michigan 



third pair are relatively longer and slenderer and the hind tar- 

 sus without the claws is only about two-thirds as long as the 

 hind tibia, while in risi the hind tarsus without the claws is act- 

 ually longer than the shortened hind tibia, giving the leg a mal- 

 formed appearance. In pygmaciis the occipital hairs are fully 

 one-half longer than in risi (pygniaeits .35-40 mm., risi about 

 .25 mm.), while the relative difference is greater, as the occiput 

 of risi is about one-half longer (measured from frons to pos- 

 terior border of occiput about midway between the angle of 

 the eye and the median line) than pygmacns. The thoracic 

 patterns of the two species are very dift'erent (see figs, i and 

 2) ; and the male appendages and female vulvar laminae are 

 equally distinct (compare figs, plate III). Pcrpiisilliis is the 

 smallest gomphine known, with abdomen only 18 mm. long and 

 hind wing 15 mm. long. It and longistigma, which is very 

 slightly larger than risi, differ from risi in both thoracic color 

 patterns and abdominal appendages. From P. gracilis, which 

 it approaches in size, risi may be recognized by the presence of 

 the basal antenodal of the second series, which is wanting in 

 gracilis, and by the very different thoracic pattern (see figs. 7 

 and 8, Ueber Gomphinen von Sudbrasilien und Argentina, 

 Mem. Soc. Ent. Belg., XIX, 191 1, Dr. F. Ris). In the key in 

 Dr. Ris's paper referred to in the preceding sentence, risi will 

 not go in either of his two groups A and B, being separated 

 from A by the presence of the basal antenodal of the second 

 series, and from B by the small number of two-celled rows of 

 cells proximal to the triangle in the anal field of the front wing. 



The small species, P. lepidus, belongs in Ris's group A, and 

 it is separated from risi, in addition to the venational difference, 

 by the very dift'erent thoracic pattern and male abdominal ap- 

 pendages (see Ris's figs. 9 and 10). In Calvert's key to the 

 Central American species of Progomphus (Bio. Cent. Am.), 



