THE COMMON FLEA 253 



its length by an exceedingly minute canal. This is 

 situated in the centre, and on each side of it are the 

 mandibles in the form of two straight flat blades, point- 

 ing downwards, and notched on each side like a double 

 saw. The mandibular teeth number about 75 in each 

 row on each side, which, at the rate of two double rows 

 to each mandible, gives a total of some 600 glistening, 

 tooth-like projections on these weapons alone. The 

 maxillae are two sharp-pointed triangular pieces, which, 

 when seen in profile, as in a specimen mounted for the 

 microscope, have the appearance of a sharp beak ; they 

 are furnished with a pair of long four-jointed palpi, 

 which project in front of the head, and might easily be 

 mistaken for antennae. The labium is reduced to a small 

 membranous plate, which carries a pair of palpi, not 

 quite so large as those of the maxillae; each of these 

 is formed into a keen blade on one edge, and rather 

 obscurely jointed into four on the other. It is not easy 

 to say exactly how these organs are used, since whenever 

 we are consciously subjected to their operation, we are 

 more anxious to get rid of the operator than to examine 

 minutely into its method of proceeding. The whole 

 evidently constitutes a piercing apparatus of exquisite 

 delicacy, and the mandibles are no doubt the most 

 effective part. We are accustomed to speak of flea-bites, 

 but this is scarcely a correct way of designating the 

 operation : the appendages of the mouth are not in any 

 sense biting organs ; the action is that of vertical pierc- 

 ing, not lateral pinching or nipping. In possessing 

 palpi, fleas agree with flies, and differ entirely from 

 the other chief order of insects with a piercing, 

 suctorial mouth, viz., the bugs, which are never pro- 

 vided with such organs. On the other hand, in pos- 

 sessing both labial and maxillary palpi, they differ from 



