652 ZOOLOGY SECT 



(reckoned as 1) the muscular force of an Insect bears a ratio to 

 its weight of from about 14 to about 23. Insects ar" also dis 



eS TheT ng ^ ^ bl » te V the keennSs of th r" 

 senses Ihe sense of sight is, as we should expect from the 

 e aborate character of the optic' organs, the most highly deveToped 

 many Insects having been shown by experiment to have a keen 

 sense of colour; but a sense of smell, the seat of which Ts in the 

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



FI °" 531 - H01 -- bee ( ^l?S»n«T«^S e); ' 



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

 developed sense of taste. A sense of hearing does nTapraa? to 

 be universally present, but is well marked in such forms aTproduce 

 sounds At the same time Insects are remarkable fo ^he instincts 

 often leading to results of an elaborate character, wW^S 

 them in the pursuit of food and the protection and reariS of 

 their young Among the insects which are the 1st Shlv 

 endowed m this respect are some-the Ants Bees Wasns ,nH 

 Termites-which live together in organised a^ti^Tc^m 

 mimities, the various individuals composing which ared^tW.T" 

 able into smtal individuals, neuter KfJd Sf^^I 



Pig. 532.-Bed Ant (Pormica rufa); 



male, worker, and female. (After Brehm.) 



and 532), each specially organised for the part which it has to play 

 in the economy of the community V J 



Distribution in time.-The earliest known fossil remains of 

 Insects have been found in rocks of Silurian age. A good many 

 fossil Insects have been found in the Devonian; bu/they on"v 

 become abundant in the Carboniferous. All the PateozoicTnsec I 

 belong to a group which has been regarded as a distinct order 

 and has been named the Palceodictyoptera. The members of thTs' 



cSte a Sti:tr teris ^, rather b ^ he absence ^ thT ts 



characteristics of any of the existing orders than by any positive 



