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OUR HOUSEHOLD INSECTS 



reverse of what obtains in that other nocturnal pest, 

 the bed-bug, whose body is flattened in the vertical 

 direction, and whose greatest diameter is the trans- 

 verse. This shape of body is called " depressed." Cer- 

 tain fishes present similar extremes of structure : thus 

 a skate is depressed, but a plaice or sole compressed. 

 The flea's body is covered with a hard, slippery, reddish- 



FlG. 77. Common Flea (Pulcx irritans), female ; e, epimeron ; c, coxa ; 

 t, trochanter ; /, femur ; s, tibia ; p, tarsus. 



brown chitinolis skin, showing plainly enough the division 

 into rings or segments which characterises insects and 

 other annulose animals. The head, which is rounded 

 above, is small in proportion to the size of the insect, 

 and is followed by three small and separate segments, 

 which represent the thorax ; these are again succeeded 

 by several much larger segments forming the abdomen, 

 which, in the female, is at least three times as deep as 



