332 PTILOTA. 



It wiW be seen by this figure, firstly, that each group con- 

 sists of five divisions (whence the system has been termed 

 the quinarian system) ; secondly, that the series of orders 

 in each group consists of a circular series of affinities; 

 thirdly, that by means of the parallel lines, the series of 

 analogical relations are kept up. Moreover, each order was 

 supposed to be connected with the two adjacent orders, by 

 means of intermediate osculant orders, such as the Strepsi- 

 j)tera, &c. Modifications of this system have been subse- 

 quently proposed by Messrs. Swainson aud Ne^vman, which 

 it would occupy too much space here to detail. 



Although, in my Introduction to the Modern Classification 

 of Insects, I have adopted a mode of arrangement founded 

 for the most part upon that of Mr. MacLeay, it may, per- 

 haps, be more useful in the present work, to present to the 

 reader the most recent classification proposed by Latreille, 

 especially as the views upon which my arrangement of the 

 orders subsequent to the Coleoptera is founded, are not yet 

 laid before the public. 



The following is, therefore, the arrangement of the winged 

 insects published by Latredle, in his Cours d'Entomologiey 

 which appeared shortly before his decease (the characters 

 being abridged), 



I. Wings, none ; metamorphoses complete; mouth sucto- 



rial. (Parasites. The flea.) 

 Order Siphonaptera (or more properly Aphaniptera, 

 Kirby; Suctoria, De Geer; Aptera, MacLeay.)* 



II. With wings, which are sometimes, however, obsolete ; 



eyes facetted, and occasionally with ocelh. 

 1. Elytroptera. Posterior wings covered by the crus- 

 taceous or coriaceous anterior pair. 



* The apterous order Aphaniptera, ICirby {Siphonaptera, Y&treiWe; 

 Suctoria, De Geer ; Aptera, MacLeay), is united by Latreille with the 

 Thysanura and Anoplura, and formed into a primary division of the true 

 insects. 



