240 
THE LIVING WORLD. 
The Phasmidae, (called walking leaves, or walking sticks) is specially 
interesting as illustrating the adaptation of animals to the conditions of their 
life, and have a close 
relation with the viantidce . 
The Ephemeridae, 
or May-Flies, are so- 
called because of the 
momentary duration of 
their existence. Their 
delicacy and grace are 
very striking, and to 
some extent atone for 
their annoyance to one 
who is not engaged in. 
the study of Natural His¬ 
tory. They furnish a 
means of subsistence es¬ 
pecially for fishes; in 
some parts of the world, 
where their number is 
very great, they are con¬ 
verted by the farmer into 
fertilizers. A few species 
are carnivorous, but most 
of the ephemetidce sur¬ 
pass the vegetarian in 
abstinence, as they add 
plants to the articles of 
food interdicted by their 
laws. At first sight it 
would seem a needless 
cruelty for an animal to 
live so short a life, and 
to find his mission in 
furnishing food for fishes. 
But this life is but the 
flashing up of a flame 
before it expires, the fire 
having been long in burn¬ 
ing, for in their prepara¬ 
tory state the ephemeridce 
have lived from ten 
months to three years, so 
migrating locusts (nat. size) {Pachytylus migratorius). that they have had time 
to enjoy the pleasures 
and fulfil the mission of a reasonably extended existence. These insects moult 
an unusual number of times, eight being no uncommon number and twenty- 
one occurring in one species. 
The Locustidse include winged and wingless species. The wings are 
