EPHEMERIDA 



127 



tries or under leaves, and in the spring they are sometimes 

 found in large numbers on the surface of pools of water or upon 

 the snow. 



Campo'dea staphyli'nus, which is regarded as the most primitive living 

 insect, belongs to this order. It is about j inch long, white, wingless, 

 and flat. Its body is exceedingly 

 soft and delicate. It is widely dis- 

 tributed. 



The "fish-moth" (Lepis'ma sac- 

 chari'na] of the house (Fig. 98), which 

 is neither a moth nor a fish, is sil- 

 very white, with a yellowish tinge 

 on antennae and legs. It is about 5 

 inch long, has .three long caudal ap- 

 pendages, and feeds chiefly upon 

 sweet starchy materials, often at- 

 tacking starched clothing and the 

 paste of wall-paper and book-bind- 

 ings. It may be gotten rid of by 

 sprinkling fresh pyrethrum powder 

 in the places infested or by spraying 

 slightly with nicotin or formalin. 



The "spring-tails" (Collem'bola) 

 have a forked spring attached to the 

 next to the last segment of the ab- 

 domen, by means of which they leap 

 from a few inches to a foot in the air. 

 The " snow-fleas " collect in large 

 numbers on the snow in spring. 

 They are often a cause of great an- 

 noyance where maple sugar is made. 



Surely the insects of this Fig. 98. Lepis'ma saccharfna, 

 order, by their simplicity of 

 structure and their similarity 

 of somites, show their worm ancestry, though some species 

 show much more complexity of structure. It will be interest- 

 ing for the student to consider how, from such a generalized 

 primitive form as Campodea staphylinus, nature can produce, 

 by modification of parts, an insect of highly complex structure. 



ORDER n. EPHEMER'IDA 



The May-flies, in the adult form, are insects of a day, but 

 they pass two or three years in the larval stage. When they 

 emerge from their larval condition into their winged form 



