29G STATES OF INSECTS. 



hour, in some even an hour. A few species, such as 

 Sphinx (Enotherce F., require several hours, or even a 

 dav, for this operation ; and, from the distance to which 

 they creep before it has taken place, a considerable de- 

 gree of motion seems requisite for causing the necessary 

 impulse of the expanding fluids a . In a few genera, how- 

 ever, as the gnat, the gnat-like Tipulidse, and the Ephe- 

 mera, this process is so rapid and instantaneous, that the 

 wings are scarcely disengaged from the wing-cases before 

 they are fully expanded and fit for flying. These genera 

 quit the pupa at the surface of the water, from which, 

 after resting upon it for a few moments, they take flight: 

 but this would evidently be impracticable, and immersion 

 in the fluid, and consequent death, would result, were not 

 the general rule in their case deviated from. 



Some species of the last of these genera, Ephemera, 

 are distinguished by another peculiarity, unparalleled, as 

 far as is known, in the rest of the insect world. After be- 

 ing released from the puparium, and making use of their 

 expanded wings for flight, often to a considerable di- 

 stance, they have yet to undergo another metamorphosis. 

 They fix themselves by their claws in a vertical position 

 upon some object, and withdraw every part of the body, 

 even the legs and wings, from a thin pellicle which has 

 inclosed them, as a glove does the fingers ; and so exactly 

 do the exuviae, which remain attached to the spot where 

 the Ephemera disrobed itself, retain their former figure, 

 that I have more than once at first sight mistaken them 

 for the perfect insect. You can conceive without diffi- 

 culty how the body, and even legs, can be withdrawn 



a Brahra, Insek. ii. 423. 



