82 Elementary Manual of Zoology. 
Examine a full-grown specimen carefully with the help of a hand lens. 
Notice that the whole animal is covered with plates of a firm, hard sub- 
stance (chitin), which encases the body and limbs like armour. Notice 
the joints, where the plates are replaced by soft skin, so that the animal 
is able to bend its body and limbs freely. This armour is found in all 
arthropods; it serves at once to protect the body and to support the 
muscles, 
Make out the three regions of head, thorax, and abdomen. The 
head is the small box-like portion in front which bears the mouth, eyes, 
and long jointed feelers (antenne). The thorax is the middle portion 
of the body. Itis covered by three rings of plates, which divide it into 
three well-marked portions (segments), which can easily be made out. 
The front segmevt (prothorax) is covered above hy a broad plate with 
yellow markings on it. Below it bears a pair of long jointed legs. The 
second segment (mesothorax) is smaller ; to its upper (dorsal) surface 
are attached the front pair of wings, while to its lower (ventral) surface 
are attached the middle pair of legs. The third segment (metathorax) 
is very similar to the mesothorax ; to its dorsal surface are attached the 
hind pair of wings, while to its ventral surface are attached the third 
(last) pair of jointed legs. 
The abdomen consists of a number of segments (the students will 
be able to count about nine of them), telescoped into each other. The 
last segment bears a pair of jointed appendages (anal cerci) attached 
to its sides. 
Notice that the specimens are of two kinds :—— 
(i) Males, with a little pair of styles attached to the ventral 
surface of what looks like the eighth, but what is really 
the ninth, seement of the abdumen.- 
(2) Females, without anal styles, but with a large genital pouch, 
with slit-like orifice, on the ventral surface of the hinder 
sepments of the abdomen. 
Examine the legs and notice that they are very similar to each 
other in structure, each consisting of the following joints :— 
(1) A large basal joint (coxa). 
(2) A minute second joint (trochanter), 
(3) A third joint (femur), to which are attached a few short 
bristles. 
(4) A fourth joint (tibia), with numerous large bristles. 
(5) A series of small joints (tarsus), with a pair of terminal claws, 
The last tarsal joint (pulvillus), which bears the claws, 
is minute. 
Examine the wings and notice that they consist of thin membrane, 
supported by numerous nervules. 
