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Vol. XXXI. LONDON, SEPTEMBER, 1899. No. 9. 



OPHIOGOMPHUS. 



BV JAMES G. NEEDHAM, LAKE FOREST, ILL. 



This genus of dragon flies is one of the groups whose members are 

 accounted rare in colleclions, though quite abundant in nature. With the 

 exception of three species, two of which have only been obtained in 

 numbers by breeding, few imagoes have been taken. Although I have 

 collected carefully for several years in localities where a (ew species were 

 common enough, I have seen but three imagoes at large, but I have bred 

 one species by hundreds, and have seen the exuvite upon the banks of 

 streams by tens of thousands. 



Nymphs of this genus seem to prefer the sandy or gravelly beds of 

 clear, rapid streams, flowing through rocky woods. What becomes of 

 the countless imagoes which issue from such places by night in early 

 summer I have not as yet been able to find out. 



So long as the collector of these insects depends entirely upon an 

 air net for his imagoes they are likely to remain rare in his collection ; 

 but even a single occasional capture of a good specimen may still add to 

 our knowledge of the genus, since variation is considerable, descriptions 

 are fragmentary, and specimens of most species are few. 



This paper is but an excuse for the accompanying plate (5), whose 

 figures are mainly drawn from the types of species and show the struc- 

 tures chiefly used in characterizing them. In its preparation I have had 

 free use of the Hagen collection at Cambridge and of the Lintner 

 collection at Albany — thanks to the kindness of Mr. Henshaw and of Dr. 

 Felt, respectively. This plate and the few annotations on species which 

 follow will serve to bring our species together in one view, and will also 

 indicate the chief gaps in our knowledge of them. 



Secondary sexual characters have been mainly used for separating 

 Ophiogomphus from its nearest allies, Onychogomphus (fig. 32) of the Old 

 World, and Herpetogomphus of the western United States and south- 

 ward. The most salient of the differential characters used for the two 

 American genera have been the form of the inferior abdominal appendage 



