346 MANUAL OF ZOOLOGY. 



no metamorphosis, and their multiplication is extremely rapid. 

 Many Mammals are infested by Lice, the same animal often 

 being subject to the attacks of more than one species of Louse. 

 Three species commonly attack man viz., Pediculus human-its 

 corporis, P. capitis, and P. pubis ; and a fourth species (P. 

 tabescentiwn) is of rare occurrence, and gives rise to the loath- 

 some disease known as Phthiriasis. 



The Lice are now very commonly associated with the 

 Hemiptera, of which they are regarded as constituting a 

 degraded and aberrant group. 



ORDER II. MALLOPHAGA. Minute Aptera, in which the 

 mouth is formed for biting, and is furnished with mandibles 

 and maxillcz. 



The members of this order (fig. 180, B) are commonly known 

 as " Bird-lice," being parasitic, sometimes upon Mammals, but 

 mostly upon Birds. They strongly resemble the Pcdiculi, but 

 the mouth is formed for biting, to suit their mode of life 

 since they do not live upon the juices of their hosts, but upon 

 the more delicate tegumentary appendages. They are some- 

 times regarded as constituting a degraded group of the 

 Hemiptera. 



ORDER III. COLLEMBOLA. Minute Aptera, with a semi- 

 masticatory or suctorial mouth ; the first abdominal segment fur- 

 nished with a ventral tube or suctorial organ; the last abdominal 

 segment but one with appendages for leaping. 



This order has been established by Sir John Lubbock for 

 the reception of a number of Insects generally known as 

 " Spring-tails." Their scientific name is in allusion to the 

 fact that they attach themselves to foreign bodies by a ventral 

 suctorial tube, which contains a viscous fluid; whilst their 

 popular name refers to their possessing saltatory appendages 

 attached to the last abdominal segment but one. These ap- 

 pendages (fig. 1 80, D and F) consist of a long forked process 

 which is generally bent along the under surface of the body, 

 and kept there by a small catch. When released, the sudden 

 extension of the elastic process throws the insect into the air. 

 The body is covered either with hairs or scales, and the latter 

 exhibit under the microscope very elaborate and beautiful 

 markings (fig. 163, E). They are generally to be found in 

 moist dark places in gardens, or on the surface of pools, 

 and the commonest genera are Podura, Smynthurus, and 

 Degeeria. 



ORDER IV. THYSANURA. Minute Aptera, with a mastica- 

 tory mouth ; the end of the abdomen furnished with long bristle- 

 like terminal appendages, used in locomotion. 



