x PHYLUM ARTHROPODA 253 



the Invertebrata by the keenness of their senses. The 

 sense of sight is, as we should expect from the elaborate 

 character of the optic organs, the most highly developed, 

 many insects having been shown by experiment to have a 

 keen sense of colour ; but a sense of smell, the seat of which is 

 in the antennae, can be shown to exist in a high degree, and 



FIG. 149. Honey bee (Apis melliflca). a, queen (perfect female) ; b, worker (im- 

 perfect female) ; and c, drone (male). (After Brehm.) 



the parts about the mouth bear nerve-endings concerned in a 

 well-developed sense of taste. A sense of hearing does not 

 appear to be universally present, but is well marked in such 

 forms as produce sounds. At 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 



FIG. 150. Red ant (Formica rufa). Male, worker, and female. 



and the protection and rearing of their young. Among 

 the insects 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 composing which are distinguishable into sexual 

 individuals y neuter workers, and soldiers (Figs. 149 and 150), 



