2 MODERN CLASSIFICATION OF INSECTS. 



of weight to that system in which they are regarded as distinct, over 

 the numerous other methods which have hitherto been proposed 

 from time to time, of some of the more celebrated of which it will 

 be convenient to give a very short notice. 



Linna3us and his disciple Fabricius introduced into the great 

 division of Insects, not only those subject to metamorphoses and 

 the acquisition of organs of flight, but also all other articulated 

 animals possessing articulated legs, which formed in the Linnaean 

 system the order ^/»fera, but which Fabricius separated into sev^eral 

 other classes. In the former of these systems we perceive the great 

 disadvantages attendant upon the employment of a single character 

 in our attempts to arrange zoological objects, since the order Aptera 

 regarded as equivalent in rank with the orders CoFeoptera, Lepidop- 

 tera, &c., comprised not only apterous hexapod, and polypod insects, 

 but also Crabs and Spiders, which more recent anatomical investi- 

 gations have proved to be respectively groups of equal rank with all the 

 winged orders united together. The elaborate researches of Cuvier 

 in comparative anatomy fully proved, that the Crabs and other allied 

 animals (genera — Cancer, Oniscus, and Monoculus, Linn.) could 

 not be retained amongst insects, inasmuch as they possessed a totally 

 distinct system of respiration, breathing by means of bronchiae or 

 gills, as well as a complete system of circulation : of these, therefore, 

 he formed the class Crustacea, which has been regarded as distinct 

 by all subsequent entomologists. Lamarck on similar grounds removed 

 the spiders, and some other species of Apterous insects (genera — 

 Aranea, Scorpio, and Phalangium Linn.), constituting them into the 

 class Arachnida, including therein, however, the Mites (G. Acarus, 

 Linn.), which breathe by means of tracheae ; the Centipedes (G. 

 Scolopendra and lulus Linn.), the spring-tailed insects (G. Lepisma, 

 and Podura Linn.) ; and the Lice (G. Pediculus Linn.*) These 

 four last-mentioned groups have much perplexed systematists, 

 none of whom are agreed as to their location, and by several of 

 whom their situations have been frequently altered. By Dr. Leach f 

 the Mites were raised to the rank of a distinct class, under the 

 name of Acari; the Centipedes were also elevated to the rank of 

 a class under the name of MyriapodaZa^m/^e ; whilst the spring- 



* The two remaining Linnaan genera are, Piilex (the flea), subject to metamor- 

 phosis ; and Termes, which belongs to the order Neuroptera. 

 f In Samouelle's Comp. p. 7.5. 



