LICE. 375 



ANOPLURA (Lice). 



The natural transition from the Acari or mites, is to the 

 Anoplura or lice. The step, however, is a wide one. It is from 

 the spiders to the true insects, from the eight-legged to the six. 

 legged class, and a good deal of the apparent affinity or similarity 

 of habit between the two is not real affinity, but mere coincidence 

 in power and place of annoyance. Entomologists have felt diffi- 

 culty in deciding to what class of insects the lice most nearly 

 belong, and the majority have placed them apart as an indepen- 

 dent order. Theoretically, we prefer the views of those who place 

 them among the Hemiptera or Bugs, although practically it is 

 more convenient to treat them as one of the sections of the 

 Aptera. Like the bugs, they have no true metamorphosis, and 

 the points on which they differ are all capable of reconciUation 

 with affinity with them. They have no wings ; but the females of 

 the scale insects (which are Hemiptera) are also wingless ; one 

 difficulty which has puzzled some is, that those lice that feed on 

 the blood of animals have, as is most fit they should, a sucking 

 apparatus instead of jaws or mandibles, while those that feed on 

 feathers or hair have mandibles, so that systematists, of whom we 

 speak, have been driven to break up the order into two, and carry 

 the sections with different feeding apparatus into different orders 

 standing wide apart. It is well known, however, that all the 

 parts of the mouth of an insect, whether they be adapted for 

 cutting, grinding, biting, or sucking, are all modifications of the 

 same parts. We therefore are not influenced by this adaptation 

 of structure to purpose to separate insects which in all other 

 respects are so obviously closely related to each other. We take 

 the biting species as exceptional deviations for the sucking ones. 



These insects are parasitic on vertebrate animals, to which they 

 are confined. As just said they consist of two groups, one of 

 which (Mallophaga), feeds on the hair and feathers of the animals 

 on which they live, for which purpose they are provided with 



