484 DESCRIPTION OF THE MUSEUM. 



being thus called. The males and females die a 

 few hours after they have perpetuated their race. 

 But before they arrive at this state they live two 

 or three years in the water, and when in their 

 last stage myriads of them quit the liquid ele- 

 ment, and fixing upon different bodies, divest 

 themselves of their newly acquired pellicle and 

 wings, and display new ones. They may then 

 be seen fluttering in the air and over the surface 

 of the water, pairing, laying their eggs, and fall- 

 ing to the ground, sometimes in such quantities 

 as to cover it an inch thick. When the white 

 may-flies (eph. albipennis) are very abundant, they 

 present the appearance of snow on falling to the 

 ground. The e. longicauda, Oliv. (n i), is the 

 largest species of the genus, and on this Swam- 

 merdam made his very interesting remarks. It is 

 frequently found at the entrance of the rivers of 

 Holland and Germany. 



The first genus of the hymenoptera is the ten- 

 thredo, so named from the saw-edged piercer 

 with which the females are provided, and with 

 which they make incisions in different parts of 

 plants in order to deposit their eggs. The divi- 

 sion cimbex of this genus comprehend the largest 

 species of the family. We shall cite as examples 

 the c.femorata (n i), \ c. lutea (n 3), arid c. vitel- 

 lina (n 6). Their larvae when disturbed emit a 



