XX PREFACE. 



of which is placed the Anoplura ; the first two agreeing in 

 undergoing a distinct metamorphosis, but differing from 

 each other in their oral apparatus : the third differing from 

 the two preceding in not undergoing any perfect metamor- 

 phosis, but agreeing with them in containing insects, of 

 both the divisions Haustellata and Mandibulata, In 1826 

 Messrs. Kirby and Spence, in the fourth vol. of their justly 

 celebrated Introduction to Entomology, inserted a classifi- 

 cation of Insects in accordance with their views : where we 

 find our Parasites again placed in an order Aptera, but of 

 a more comprehensive character than usual, embracing 

 three sub-orders: the Hexapods (Thysanura and Anoplura 

 of Leach), the Octopods (Arachnides Tracheales of Latr.), 

 and the Polypods (the Myriapoda of Leach and Latr.). In 

 1829 Mr. Stephens produced his Systematic Catalogue of 

 British Insects, in which, under the second division of the 

 Class Insecta, Haustellata, the Lice constitute solely the 

 Order Aptera, rather a striking contrast to the preceding, 

 which included so many.* From 1835 to 1840 Dr. Bur- 

 meister published his Handbook of Entomology, and Ge- 

 nera Insectorum, containing a system of classification, and 

 descriptions of a number of species of Anoplura ; the ar- 

 rangement followed is that of Nitzsch with additions. The 

 Pediculidce, under a new order Rhynchota, and the Nir- 

 midoB under that of Mallophaga, divisions equivalent to 

 Mandibulata and Haustellata, or to the Orders Hemiptera 

 and Orthoptera. The division of the Rhynchota is in ac- 

 cordance with Dr. Leach's system into three genera : the 

 general grouping of the Genera and Sub-Genera being such 

 as meet my views. I have adopted it in this Monograph, 

 with a slight modification, viz. : retaining the Order Ano- 

 plura of Leach, and reducing those of Rhynchota and Mal- 

 lophaga to the rank of Sub-Orders. The annexed Table 

 which I have sketched will exhibit more clearly my ideas. 

 * See note t page xxiv. 



