88 Life and Immortahty. 
when the creature opens its mouth. In length the mandible 
is three times its breadth, and furnished with three sharp 
teeth on the outer edge, and with a broad cutting margin 
within, and still further inwards with a number of straggling 
small spines. The lower lip is broad and stout, with a dis- 
tinct medium suture, which indicates a former separation in 
embryonic life into a pair of appendages. Its palpi are three- 
jointed, the joints being broad, and directed backwards in 
life, and not forwards, as in the higher insecta. 
LEPISMAS AT WORK. 
How Books are Destroyed. 
Perhaps not more than a half-dozen species of Lepisma are 
known to exist in this country. Our commonest form is 
very abundant in the Middle States under stones and leaves 
in forests, and northward in damp houses, where it has much 
of the habits of the cockroach, eating clothes, tapestry, silken 
trimmings of furniture, and doing great mischief to libraries 
by devouring the paste and mutilating the leaves and covers 
of books. Our heat-loving form, which is apparently allied 
to the Lepisina thermophila of Europe, and which may be 
an imported species, is quite as destructive as its nearest of 
kin Lepisma saccharina. It does not confine its ravages to 
