12 
INTRODUCTION. 
water have hind legs more or less flattened and fringed 
with long hairs, which they use as a boatman does his 
oar; forms of these oar-like feet may be seen in Dyticus, 
ISotonecta, and Gyrinus. The mole cricket, like its 
mammalian namesake, has its fore legs very short and 
strong, the tibia being cut into finger-like projections 
suited to its burrowing habits; in the water scorpion 
(Nepa cinerea) the fore legs are converted into a pair 
of nippers, by means of which the insect seizes and 
retains hold of its prey. 
The wings of an insect are beautiful and interesting 
objects ; they are attached to the second and third 
segment of the thorax; each wing consists of two 
membranes with a number of veins or nervures between 
them, which ramify in various directions and help to 
keep the wings extended. Some insects have only two 
wings, others (the greater number) have four, which are 
either of a similar texture throughout, and are all 
available in flight, or else the anterior pair have a con¬ 
sistency like horn, and form a sheath or .covering 
for the hinder wings when the insect is at rest; when 
in flight these wing-cases are kept still, being at right 
angles with the body. These are known by the name 
of Elytra , from the Greek tXvrpov “ a cover” or “ case,” 
used for the shard of a beetle’s wing as early as the 
time of Aristotle. All beetles ( Coleoptera )—not the 
so-called “ black beetles” of our kitchens, which are 
not beetles at all—possess these horny pair of wing 
covers, hence the term which has been given to the 
order, from ko\i6q “a sheath,” and ^np6v “a wing.” 
In some insects the basal part of the elytra is horny, 
the top part being membranous. The Diptera or 
