EPHEMERIDA. 215 



and chewing; and the larvae seem well able to protect 

 themselves, being able to act on the offensive as well as 

 being warily defensive. During this stage the insect 

 fares as well as do most other insects ; it is only in the adult 

 stage that the insect is peculiarly a weak insect. Finally, 

 at the end of a year, or two or three years for some species, 

 the nymph is ready for the last moult. It breathes while 

 in the water by means of flat, leaf -like gills, extending 

 into the water from either side of the body along the 

 entire abdomen and in some species from the thorax also. 

 Some very young nymphs are without these lateral 

 appendages, and seem to make the exchange of carbon 

 dioxid for oxygen through the delicately thin body skin, 

 which is at that time without chitin. 



Having reached the adult nymph stage, the old 

 nymph floats to the water surface, or crawls out onto the 

 bank, begins to dry, the skin splits, and out comes the 

 adult May fly. Others appear in rapid succession, so 

 that there is soon a swarm of these delicate creatures; 

 then all join in the whirling dance over the river surface, 

 or under some electric light if there is one near. If the 

 swarm belongs to the short-lived May flies, the mating 

 occurs during this dancing flight, the females drop their 

 egg packets, and soon flutter after them and fall into the 

 water, the frail adult life over and done before the coming 

 of another sunrise. It is because of the shortness of the 

 adult life of the most of the species that the name of the 

 order is given. Ephemerida is made of the Greek 

 preposition y ephi, meaning during, and the Greek noun 

 emera, meaning a day. 



No May fly, so far as known, lives beyond the third 

 day; and three days is an unusual period, the majority 

 of our May flies living only a few hours. With some few 



