x PHYLUM ARTHROPODA 251 



the same time Insects are remarkable for the instincts, often 

 leading to results of an elaborate character, which guide 

 them in the pursuit of food and the protection and rearing 

 of their young. Among those which are the most 

 highly endowed in this respect are some the Ants, Bees, 

 Wasps, and Termites which live together in organised 

 associations or communities, the various individuals compos- 

 ing which are distinguishable into sexual individuals, neuter 

 workers, and soldiers, each form specially organised for the 

 part which it has to play in the economy of the community. 



4. THE MYRIAPODA 



The class Myriapoda, including the Centipedes and the 

 Millipedes, consists of tracheate Arthropoda, which bear 

 many features of resemblance to the Insects. There is a 

 distinct head, bearing many-jointed antennae, a pair of eyes, 

 and two or three pairs of jaws ; and a body, not distin- 

 guishable into regions, but consisting of a number of 

 similar segments, each bearing either one or two pairs of 

 legs. A system of air-tubes or tracheae similar to those of 

 Peripatus and the Insects open by a series of stigmata, 

 usually in considerable numbers, on the sides or lower 

 surfaces of the segments. 



The head in the Myriapoda (Fig. 139) is as well marked 

 off as in an Insect ; it appears to be composed of about 

 four fused segments. The antenna consist sometimes of 

 many, sometimes of comparatively few segments. A pair of 

 eyes situated on the dorsal surface of the head, consist of 

 aggregations of ocelli except in the genus Scutigera, in which 

 there are compound eyes, differing, however, in their structure 

 from those of Insects. There is a movable labrum, a pair of 

 mandibles, and two pairs of maxilla. The mandibles have 



