382 THE APHANIPTERA^ 



blood, is of a rather long, compressed form, with a 

 small head, and a thorax and abdomen distinctly di- 

 vided into segments. On the sides of the head we see 

 a pair of small eyes, and from the front of it projects 

 a pair of articulated organs composed of four joints, 

 which at first sight would be taken for antennae, 

 but which are really the maxillary palpi. Below 

 these we find the parts of the mouth itself, those for- 

 midable weapons with which this apparently con- 

 temptible foe contrives sometimes to harass us so 

 terribly, and even to banish sleep from our eyes. 

 These consist of a pair of sword-shaped mandibles 

 with finely serrated edges, and of a long slender bristle 

 which is supposed to represent the labrum, sheathed 

 by a pair of three-jointed labial palpi of considerable 

 size, the labium itself, like the maxillae, being very 

 small. The true antennae of the Flea are minute 

 organs placed in small cavities on each side of the 

 head behind the eyes, and these in many species ap- 

 pear to be closed by small valves. The legs are long 

 and stout, especially the hinder pair, by the agency 

 of which the Flea is enabled to perform those extra- 

 ordinary leaps for which he is so celebrated, and in 

 Avhich it is calculated that he frequently passes over 

 at least two hundred times his own length. The 

 body and limbs of the Flea are beset with numerous 

 short bristles, and his integuments, as most of us are 

 aware by experience, are of so firm a nature, that it 

 is not easy to make an impression upon them with 

 the finger and thumb. 



But our little enemy did not always possess the 

 form under which he makes his attacks upon our 

 bodies. In the first period of his existence he is a 

 long footless grub, composed of thirteen segments 



