252 



NEW YORK STATE MUSEUM 



been studied and collected suflficiently for the determination of 

 this matter. It would be utterly impossible at present to give 

 a key that would distinguish females, and a key for the males 

 based on coloration would have to be offered tentatively, since 

 the range of variability in color pattern has not been determined. 

 Instead of attempting a key, I have thought best to present 

 herewith drawings of the appendages of the male of all species 

 known from the State, these being the surest criteria for the 

 recognition of the species. The males can then be determined 

 by comparison with the figures, and the females can be kept 

 with the males with which they are found associated in nature. 

 As is to be expected in such a genus, the nymphs are very 

 much alike. A brief general description here will therefore save 

 much repetition in treating of the species. 



Nymph. The nymph of Enallagma is slender, nearly smooth,. 



with the head a third wider than succeeding parts of the body 



(th^ excess of width being wholly due 

 to the lateral prominence of the eyes)^ 

 and with abdomen very slightly taper- 

 ing posteriorly. The head is one half 

 wider than long, with frons moder- 

 ately prominent, broadly rounded hind 

 angles, and a wide posterior excava- 

 tion between them. Antennae long,, 

 slender, seven jointed, the segments 

 increasing in length to the third, and 

 decreasing thereafter to the tip. Legs 

 slender, nearly smooth, often banded 

 with brown. Wing cases reach pos- 

 teriorly to the middle of the fourth 

 abdominal segment. Abdomen cylin- 

 dric, its segments decreasing a very 

 little both in length and in diameter 

 toward the apex. Gills lanceolate,, 

 pointed, with variable color pattern. 



Labium slender, with prominent: 

 median lobe, lateral lobes upcurved at 

 their external margins; mental setae 

 two to four each side. Lateral setae 

 four to five each side. Lateral lobe 



with a moderate movable hook and an arcuate end hook and 



several small teeth on the distal end above the latter, of variable 



DroBortions. 



Fig 10 The nymph of Enallagma 

 signatum:.^, lateral view of median 

 gill lamella. 



