268 



INTRODUCTION TO ZOOLOGY 



by appendages, as shown in Fig. 200. The insect cleans 

 its antennae by dragging them between its jaws. 



The thorax has the usual three segments, but the first of 

 these has a more independent motion than is general in 

 insects, owing to the specially free articulation between it 

 and the second segment. 



The jointed legs, borne ventrally on the thorax, are long 

 and strong. The third and fourth joints (femur and tibia) 

 are beset with stiflf bristles, with which the body is brushed 

 and kept clean. 



The foot or tarsus is five-jointed, each joint having a 

 velvety pad beneath it ; the last also bears two claws, and 

 between these is a special pad which may act like that on 



Fig. 200. — The Mouth-parts of the Common Cockroach, 

 mud, Mandible ; a 6 has been removed from a! h' ; mx, maxilla ; mx.ls^ maxillary 

 lobes ; mx.palp, maxillary palp ; m, mentum bearing labial palp, Lp, and the 

 labium, IJ). The central lobe of the labium, the lingva, can be faintly seen. 



a fly's foot (p. 330), enabling the insect to run up smooth 

 vertical walls. 



The abdomen is large, broad, and clearly segmented, but, 

 owing to the varying degree to which, at different ages 

 and in different sexes, some of these segments are retracted 

 within others, the number to be seen in a casual external 

 examination varies in different specimens. It is said that ten 

 segments actually exist. 



From the sides of the last^ segment project little tactile 

 processes known as the " cerci anales," and in the adult males, 

 and the young larvae of both sexes, this segment bears as 

 well two small slender "styles" which can be just distinguished 



^ In rig. 199, the shading of the last segment makes it appear as if 

 it were itself segmented, but this is not so. 



