EPHEMERA MARGINATA. 6^ 



its body, and its tail, for the purpose of rowing and ba- 

 lancing itself, and two other paddles for steering, making 

 in all fourteen. Even when the creature is at rest, if in 

 health, all except the lowest two, or steering paddles, are 

 in rapid motiona circumstance which renders those 

 beautiful ramifications of the air-vessels shewn in the 

 drawing, figure 4, difficult to be viewed while the larva 

 is alive. 



Independent of its locomotion, by means of its legs, pad- 

 dles, and tail, it possesses a power of leaping or spring- 

 ing in the water, which it effects by incurvating its body 

 backwards, and then suddenly straightening it, by which 

 kind of motion it raises itself to the surface of the water 

 with great celerity. 



When the crysalis approximates to its perfect state, it 

 swims more elegantly : its motions now appear entirely 

 subservient to its will, and at the same time it leaps with 

 greater velocity. Within a few days, however, of its 

 change, it becomes rather sluggish, and attaches itself to 

 the stalks of water-plants, on which it will remain for 

 hours together, if undisturbed, only moving its paddles 

 at intervals. 



At the period of its transformation to the perfect state, 

 some parts of the insect assume a metallic lustre, as if 

 the space between the crysalis (which may now be called 

 the case of the animal, every part of the latter being 

 perceptible through it,) and the inclosed insect, were 

 partly filled with mercury. This appearance is ultimately 

 extended over the whole body, and is occasioned by a 



