216 MANUAL OP ZOOLOGY. 



rally solitary in each community fulfil no other function save 

 that of laying eggs. All the other duties which are necessary 

 for the existence of the community are performed hy the 

 workers, or neuters. 



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 

 meamorphosis, 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 condi- 

 tion, 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 (Pediculi). 

 The common Louse is furnished with a simple eye, or ocellus, 

 on each side of a distinctly differentiated head, the under sur- 

 face of which bears a suctorial mouth. There is little distinc- 

 tion between the thorax and abdomen, but the segments of 

 the former carry three pairs of legs. The young pass through 

 no metamorphosis, and their multiplication is extremely 

 rapid. 



