166 INVERTEBRATE ANIMALS, | 
nished with bristles, by the sudden straightening of which the 
insect can effect powerful leaps. In many cases the body is 
covered with delicate scales, which form beautiful objects under 
high powers of the microscope. 
SECTION II. HEMIMETABOLIC INSECTS.—MWetamorphostis in- 
complete; the larva differing from the perfect insect chiefly in 
the absence of wings and in size; pupa usually active, or, tf 
gutescent, capable of movement. 
ORDER IV. HEMIPTERA.—In this order the mouth is formed 
for suction (fig. 78, 3); the eyes are compound, but simple eyes 
are often present in addition. ‘Two pairs of wings are always 
present, 
Fig. 81.—Hemiptera. Bean Aphis (Ap/%2s fade) ; winged male and 
wingless female. 
The Hemiptera live upon the juices of plants or animals, 
which they are enabled to obtain by means of their suctorial 
mouths. All the four wings are present, but the condition of 
these varies in different sections of the order. In one group 
all the four wings are membranous (fig. 81); but in the other 
the posterior wings and the tips of the anterior wings alone are 
membranous. The inner portions of the anterior wings are 
hardened by chitine, and they are known as “ hemelytra” (Gr. 
hemt, half; and e/utron, a sheath). Amongst the moré fami- 
liar examples of the Hemiptera are the numerous species of 
Plant-lice (Aphides), the Field-bug (Pentatoma), the Boat-fly, 
the Cochineal insects, and the Cicadas. 
The Cochineal insects are of considerable commercial 
importance, as_ the dried and powdered bodies of the female 
constitute the substance known as Cochineal, from which is 
