87 



questionable nymphs oi plagiatus. Walsh apparently included 

 both species in \\\^ fuvialis, described from specimens collected 

 about Rock Island, but his statements of the habits oi JiuriaJis, 

 which are quite unlike those we have recorded for plagiatus, 

 very likely apply to nofafus, and may account for its apparent 

 rarity. He says that while fratenius and rasfHs haunt the land 

 and are easy to c^])ti\Ye,fliiviaIis "makes long excursions to and 

 fro on the surface of the river, scarcely ever approaching the 

 land except for a second." 



Williamson ('01b) lists the species from Illinois, Michigan, 

 Ohio, Tennessee, and Quebec, Canada ; June 1 and 21 in Ohio 

 and Michigan, and September 30 in Tennessee. 



21. Gomphiis spiniceps Walsh. 



Macrogomphtis? spiniceps Walsh, '62, p. 389 (female). 

 Gomphus spiniceps, Kellicott, '95, p. 209 (male). 

 Gomphus segregans, Needham, '97, p. 185 (male). 



This seems to prefer somewhat rapid currents. Excepting 

 a single example from the Illinois River, the nymphs appear in 

 the Laboratory and Biological Station collections only from 

 Quiver Creek and Quiver Lake near the mouth of the creek.* 

 This creek is a peculiar and beautiful stream, shallow and 

 sandy, fed by springs of soft water flowing out of the sand 

 beds, and hence quite uniform and constant in its flow. At 

 the mouth of this stream spiniceps is associated with externus 

 and plagiatus. The nymph agrees with that of plagiatus in 

 having no dorsal elevation or hooks except a single rudimentary 

 posterior tooth on the penultimate segment, but differs from it 

 conspicuously in the form of that segment, which is long and 

 narrow, the lateral margin fully twice the basal width. In this 

 character it resembles Gouiphits paUidiis, but has not the elevated 

 dorsal ridge nor the long tenth segment of that species. As 

 in the case of plagiatus and externus, nymphs placed in breed- 



*Numerous exuviae and emerging individuals have since been taken on the 

 rocky walls of the shallow gorge of the Illinois River at Ottawa, July 21 and 

 August 19, the larger number of imagos being secured on the latter date. 



