278 MANUAL OF ZOOLOGY. 



ORDER II. MALLOPHAGA. Minute Aptera, in which the 

 mouth is formed for biting, and is furnished with mandibles 

 and maxillae. 



The members of this order are commonly known as " Bird- 

 lice," being parasitic, sometimes upon Mammals, but mostly 

 upon Birds. They strongly resemble the Pediculi, 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. 



ORDER III. THYSANURA. Apterous insects, usually with a 

 masticatory mouth, and having the extremity of the abdomen 

 furnished with locomotive appendages. 



The most familiar members of this order are the Podurce 

 or " Springtails," which are characterised by the possession of 

 a forked caudal appendage, by the extension of which con- 

 siderable leaps can be effected. In the nearly allied Lepismce, 

 locomotion is assisted by caudal bristles. In both, the body 

 is covered with hairs or scales, the structure of the latter 

 being often very beautiful. 



SUB-CLASS II. HEMIMETABOLA. Metamorphosis incomplete; 

 the larva differing from the imago chiefly in the absence of wings, 

 and in size; pupa usually active, or, if quiescent, capable of move- 

 ment* 



ORDER IV. HEMIPTERA. Mouth suctorial, beak-shaped, 



Fig. 108. Hemiptera. Bean Aphis (Aphis fabce), winged male and wingless female. 



consisting of a jointed rostrum, composed of the elongated 

 labium, which forms a jointed, tubular sheath for the bristle- 



* The Coccidce, amongst the Hemiptera, undergo a complete metamor- 

 phosis. In certain of the Hemiptera and Orthoptera the adult is apterous, 

 and in these cases there cannot be said to be any metamorphosis, since 

 the larvae differ from the adult only in size, in having fewer joints to the 

 antennae, and in having a smaller number of facets in each of the compound 

 eyes. 



