10 



ZOOLOGY 



folded together over the back. Dragon-flies live on the 

 wing, hovering over water and preying upon other insects, 



especially mosquitoes. The eggs develop 

 in the water into aquatic larvae which are 

 quite unlike the adult. Especially the 

 jaws are peculiar, being jointed and capa- 

 ble of sudden protrusion, in order to catch 

 the animals which serve as prey. These 

 larvee are easily reared over winter in an 

 aquarium, where not only their ferocious 

 habits, but also their peculiar method of 

 breathing by means of water taken in at 

 the anus, may be observed (Fig. 9). 



The Ephemeridae, 1 or May-flies. The 

 FIG. 9. - - JEschna, adult May-fly possesses finely veined fore 



old larva, or pupa. . 1-1 ^ ^ , i , i 



Nat. size. Photo, wings, winch are much larger than the 

 by w. H. C. P. hind wings. The mouth parts are rudi- 



mentary and the abdomen terminates in 

 two or three filamentous appendages. As their systematic 

 name implies, they have a very ephemeral existence in 

 the imago state. The imago appears in swarms early in 

 the summer and lives but a fe\v hours, eating nothing 

 and depositing eggs upon or under stagnant water. The 

 larvse feed upon small aquatic plants and insects, breathe 

 by means of gills placed on the back, and live for nearly 

 a year, or even for two or three years, in the immature 

 stages. After many moultings the apparent adult emerges, 

 but, unlike other insects, undergoes an additional moult 

 before laying its eggs. As the insect is subjected to many 

 accidents in its long and defenceless life, each species is 

 preserved only by an enormous fecundity. 



. a day, i.e. lasting but a day, short-lived. 



