55 

 II. Progomphus Selys. 



Progomphiis obscurus Ramb. 



The nymph of this species has divergent wing-pads, like 

 Diastaf omnia, but differs from all our other gomphids in the 

 proximity of the middle legs. It represents an extreme of 

 specialization for life as a burrower in the bed of running 

 streams. It has not been found in the Illinois nor in its adja- 

 cent lakes, but seems to be common in the sand of the smaller 

 rivers, such as the Spoon River and upper Sangamon. The 

 State Laboratory has a large number of examples from the 

 latter river, taken in September and October. One specimen 

 was found at the lower edge of a sand-bar in Spoon River, near 

 Havana, in July. The published dates for the nymph are April 

 (Fla.), May, and June. The adults are rare in collections, 

 although the species seems widely distributed. Perhaps the 

 peculiar habits of the nymph may be correlated with a rela- 

 tively long period of nymphal life and short period of life as an 

 imago. The adult has been taken in Indiana as early as June 

 26, and in Illinois June 29 and July 13. It is recorded from 

 Massachusetts, Georgia, Ohio, Indiana, Florida, Texas, Cali- 

 fornia, Oregon, and Mexico. 



The nymph was described and by supposition connected 

 with this species by Hagen ('85, p. 247), and the supposition was 

 verified by Mr. Needham (97, p. 184). 



The nymph measures 31 mm. ; abdomen, 20 mm. ; hind femur, 

 4 mm.; width of abdomen, 6 mm., of head 5 mm. 



Body depressed anteriorly and tapering posteriorly ; lateral 

 margins with long hairs. 



Head depressed, sloping anteriorly, cordate, broadly notched 

 behind ; hind angles rounded. Antennae inserted into cylin- 

 droid elevations on the front, depressed and incurved so as to 

 almost surround the pilot-shaped labrum ; two basal joints very 

 short ; third, twice as long as the two basal combined, slightly 

 flattened and upcurved at the tip ; fourth joint small, one third 

 to one fifth as long as the third, slender and strongly recurved. 



