142 



CONNECTICUT GEOL. AND NAT. HIST. SURVEY 



[Bull. 



4. A group comprising scudderi, amnicola and notatus, in which the 



median pale stripe of the mesepisternum is isolated and not con- 

 nected with the pale thoracic collar, and the njTnphs of which 

 are provided with obliquely truncate teeth on the labial palpi 

 (PI. V, Figs. 12, 17, 18; p. 160). 



5. The expanded abdomen types including crassus, graslinellus, fra- 



ternus, ventricosus, vastus, and extermis. The nymphs are pro- 

 vided with prominent lateral spines and the ninth segment is not 

 elongate, but wide in proportion to its length. Probably dilata- 

 tiis, lineatifrons and quadricolor also belong here (p. 162). 



6. A group containing plagiatus and spiniceps, characterized by their 



very long slender abdomens in the adult stage, and the elongate 

 terminal segments of the nymphal abdomen, particularly seg- 

 ment 9 (p. 166). 



The species G. abditus described by Miss Butler from Massachusetts is 

 apparently most closely related to lividus but it is difficult to determine just 

 where it belongs from the original description. No collectors have taken 

 this species since its description in 1914 (Can. Ent. 46: pp. 347-348). It is 

 omitted from the present paper. Quadricolor and adelphus are also omitted. 



Fig. 17. Tips of abdomens of Gomphus nymphs (A, B, and C, after 

 Needham). A. G.fraternus. B. G. pallidus. C. G. spiniceps. D. G. lividus. 



Gomphus and Lanthus 



Key to Species 

 Nymphs 



Third antenna! segment subcircular; no dorsal hooks, ridges or 

 prominences on the abdomen 2 



Third antennal segment not subcircular; either dorsal hooks, 

 ridges or prominences usually present on the abdomen 3 



Length full grown about 19 mm. (PI. iii. Fig. 9) 



(Lanthus) albistylus 



Length full grown about 23 mm (Lanthus) parvulus 



Segment 9 twice as long as wide at base ; length full grown over 

 40 mm spiniceps 



Segment 9 never twice as long as wide at base ; length full grown 

 less than 40 mm 4 



Dorsal ridge present on caudal abdominal segments ; teeth of palpi 

 long, sharp, and about equal in length to the terminal fixed 

 hook ; segment 9 as long as wide or only slightly shorter 5 



