92 ANATOMY OF AN ARTHEOPOD. 



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. 32 a, Jf). These jaws are present in all biting 

 arthropods. The first maxiUce follow the mandibles behind. 

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

 protoxjodite , (ii) endopodite ; (iii) exopiodite. 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 pal'p (Mp), is a five-jointed process, carried on the outer 

 side of the distal end of the stipes. 



The second maxillie (fig. 32, b) are very like the first, hut 

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

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

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

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

 plate, the larger one being called the suhmentum (Sab), the 

 smaller and distal one the mentum (J/e). The latter bears endo- 

 and exopodites. 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 metathorax. 



Each leg is made up of five divisions as follows : the coxa 

 (fig. 33, a), a stout, proximal, leaf-like joint, uniting the leg to 

 the body ; then follows a small joint called the trochanter (b), 

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

 is followed by a slender straight joint armed -(N-ith spines, the 

 tibia (d). The last division, the tarsus or foot (g), is con- 

 stituted of six joints in this type (Cockroach), the last tarsal 

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

 tarsal joints will be seen to vary in different groups of 

 Arthropods. 



