HUMAN PEDICULI 341 



cause or the accompaniment of the mysterious diseases 

 called pediculosis and phthiriasis, which have become so 

 celebrated through their reputed connection with some 

 of the vilest of historical personages. 



A word or two on the systematic position and classi- 

 fication of these vermin may fittingly conclude our 

 subject : this is the more necessary as there are several 

 other insects that might easily be confounded with them. 

 Pediculi are now regarded as forming a degraded section 

 of the order Hemiptera, which, as we have already seen, 

 contains the various species of bugs, &c. The nearest 

 approach to the peculiar structure of the mouth in the 

 Pediculi is certainly to be found in this order, the lice 

 differing from the rest chiefly in having the suctorial 

 trunk retractile, and capable of being completely with- 

 drawn inside the head. The lice thus bear much the 

 same relation to the rest of the Hemiptera that the fleas 

 do to the Diptera (two-winged flies) with which they are 

 now associated. The section of the order to which they 

 belong is called Anoplura ; but this term is often made 

 to include another set of parasites externally something 

 like them, but furnished with biting jaws instead of a 

 suctorial proboscis. These are the insects called Mallo- 

 phaga, or bird-lice, which devour the feathers of birds. 

 But here again we must guard against being misunder- 

 stood. It is not implied that all parasites found on 

 birds are true Mallophaga, nor that the latter are exclu- 

 sively confined to birds. As a matter of fact, birds are 

 troubled not only with the feather-eating Mallophaga, 

 but with true lice allied to the Pediculi above mentioned, 

 which suck their blood, just as the latter do that of 

 mammals. These, of course, belong to the same section 

 as the vermin whose life-history and habits we have been 

 considering. The Mallophaga, however, being biting, 



