ANNULOSA: INSECTA. 347 



The Insects of this order are closely related to those of the 

 preceding, but the long anal bristles do not form a " spring ; " 

 and the mouth is distinctly masticatory. The two principal 

 genera are Lepisma and Campodea (fig. 180, C), both of which 

 live generally under stones or in dark situations. The body 

 is hairy, or clothed with metallic scales ; these latter organs 

 being in Lepisma so delicately marked that they are com- 

 monly used as test-objects for the microscope. 



According to Packard, the Thysanura and Collembola are 

 to be regarded as degraded groups of Neuroptera, the former 

 having also affinities with the Myriapoda. According to Sir 

 John Lubbock, Campodea may be regarded as a modern re- 

 presentative of an ancient type-form, from which the higher 

 Insects originally took their rise. 



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 V. HEMIPTERA (Rhynchotd). Mouth suctorial, beak- 

 shaped, consisting of a jointed rostrum, composed of the elongated 

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

 shaped, styliform mandibles and maxilla. Eyes compound, 

 usually with ocelli as well. Two pairs of wings in most ; some- 

 times wanting. Pupa generally active. 



The Hemiptera live upon the juices of plants or animals, 



Fig, 181. Hemiptera. Bean Aphis (Aphis f aba), winged male and wingless female. 



which they are enabled to obtain by means of the suctorial 

 rostrum. 



* The Coccidtz, 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. 



