into two Classes. clxxxvii 



males : the abdomen terminates in long caudal multiarticulate 

 setae. 



The following formula, founded on the researches of Dr. Leach, 

 exhibits the characters by which these insects may be again readily 

 subdivided. 

 Wings 4 : — 



Caudal setae 2 Baetid^e, Newman. 



Caudal setae 3 Ephemerim, Newman. 



Wings 2 : — 



Caudal setae 3 Ccenid^e, Newman. 



Caudal setae 2 Cloeonid^e, Newman. 



Characters of Agrionina. 



Larva aquatic, breathing by means of an internal abdominal appa- 

 ratus, which, like the internal gills of fishes, or the external gills 

 of the Ephemerina, appears to possess the power of abstracting 

 oxygen from water, which is subsequently expelled through the 

 anal aperture with a jerk which propels the insect forward, and 

 seems to constitute its only natatory movement, although it crawls 

 on mud, stones, and the stems of aquatic plants: it has moderate- 

 ly long, filiform, 7-jointed antennae, corneous mandibles, and a 

 remarkable jointed and porrectile labium, with which it seizes the 

 small aquatic animals which constitute its food: its body is long 

 and linear, with six legs of moderate length, and three long 

 flattened caudal appendages : it is carnivorous, and excessively 

 voracious. 



Pupa in figure, habits, and food resembles the larva, but possesses 

 rudimentary wings. 



Imago with short slender antennae, usually but not constantly 

 7-jointed : transverse hammer-shaped exserted head : round 

 widely separated lateral eyes : complete manducatory mouth : 

 atrophied prothorax: cylindrical abdomen: four wings minutely 

 reticulated and all alike, their shortest diameter near the base, 

 their longest diameter at three fourths of the distance from the 

 base to the apex, the increase being uniform throughout, they 

 are held above the body of the insect when at rest, meeting 

 each other back to back : legs simple and of uniform length, 

 tarsi 3-jointed : they walk slowly and awkwardly,^// feebly and 

 heavily in the sunshine, and continue but a short time on the 

 wing : feed entirely on living insects : the tarsi are 3-jointed. 



