ANNULOSA I INSECTA. 2/7 



CHAPTER XL. 

 " DIVISIONS OF INSECTA. 



THE class Insecta includes such an enormous number of 

 species, genera, and families, that it would be impossible to 

 treat of these satisfactorily otherwise than in a treatise 

 especially devoted to Entomology. Here it will be sufficient 

 to give simply the differential characters of the different 

 orders, drawing attention occasionally to any of the more 

 important points in connection with any given family. 



As already said, the Insecta are divided into three divisions, 

 termed Ametabola, Hemimetabola, and Holometabola, according 

 as they attain the adult condition without passing through a 

 metamorphosis, or have an incomplete or complete metamor- 

 phosis. The Insects which come under the first head (viz., 

 Ametabola} are not furnished with wings in the adult con- 

 dition, and the three orders which compose this section are 

 commonly grouped together under the name Aptera. By 

 some, however, this division is entirely rejected, and the three 

 orders in question are placed amongst the Hemimetabola^ or 

 even grouped with the Myriapoda. 



SUB-CLASS I. AMETABOLA. Young not passing through a 

 metamorphosis, and differing from the adult in size only. Imago 

 destitute of wings ; eyes simple, sometimes wanting. 



ORDER I. ANOPLURA. Minute Aptera, in which the mouth 

 is formed for suction ; and there are two simple eyes, or .none. 



This order comprises insects which are commonly parasitic 

 upon man and other animals, and are known as Lice (Pedi- 

 cult). The common Louse is furnished with a simple eye, or 

 ocellus, on each side of a distinctly differentiated head, the 

 under surface of which bears a suctorial mouth. There is 

 little distinction between the thorax and abdomen, but the 

 segments of the former carry three pairs of legs. The legs are 

 short, with short claws or with two opposing hooks, affording a 

 very firm hold. The body is flattened and nearly transparent, 

 composed of eleven or twelve distinct segments, and showing 

 the stigmata very plainly. The young pass through no 

 metamorphosis, and their multiplication is extremely rapid. 

 Most, if not all, Mammals are infested by Lice, each having 

 generally its own peculiar species, and sometimes having two 

 or three. Three species are said to belong to Man viz., 

 Pediculus humanus, P. capitis, and P. pubis. 



