ANATOMY OF AN ARTHROPOD. 103 



and the mouth. The latter opens behind the labrum and be- 

 tween the jaws. The two antennas arise from two oval mem- 

 branous patches below the eyes and just in front of them. The 

 mouth is of that type known as the biting mouth. It consists 

 of a pair of stout jaws, toothed on the inner margins, the 

 mandibles (fig. 39 a, M). These jaws are present in all biting 

 arthropods. The first viaxillce follow the mandibles behind. 

 Each maxilla consists of three chief or primary parts — (i) the 

 proto'podite ; (ii) endopodite ; (iii) exopodite. The first will be 

 seen to consist of two joints, the cardo or proximal joint and 

 the stipes or distal joint. The second, or endopodite, has also 

 two parts, the inner portion or lacinia being blade-like, the 

 outer or galea soft. The exopodite, usually called the maxil- 

 lary palp {Mp}), is a five-jointed process, carried on the outer 

 side of the distal end of the stipes. 



The second maxilloi (fig. 39 b) are very like the first, but 

 small, and are fused together, forming a plate in the middle 

 line, the labium or lower lip. The structure of this lower lip 

 is easily seen in this insect. The two basal parts of the proto- 

 podites are fused in the middle line, forming a two-jointed plate, 

 the larger one being called the submentum (Sub), the smaller 

 and distal one the mentum (Me). The latter bears endo- and 

 oxopodites. The endopodites together are known as the lingua 

 (Li). The exopodites are three-jointed palps (Lp). 



Thoracic appendages. — On the thorax are three pairs of legs 

 attached to the sterna, and two pairs of wings united or articu- 

 lating with the meso- and metanota. 



Each leg is made up of five divisions as follows : the co.ea 

 (fig. 40, a), a stout, proximal, leaf-like segment, uniting the leg 

 to the body ; then follows a small segment called the trochanter 

 (b), which unites at its distal end with the femur (c), which in 

 turn is followed by a slender straight segment armed with 

 spines, the tibia (d). The last division, the tarsus or foot (g), 

 is constituted of six segments in this type (Cockroach), the last 

 tarsal bearing a pair of claws or ungues (h). The number of 



