CHAPTER XI 



BEHAVIOUR 



The work of Lorenz, Tinbergen, Thorpe, Lack and others in 

 recent years has thrown much hght and insight into the behavioural 

 characteristics of vertebrates, particularly mammals and birds. 

 Observations by Pantin, Blest, Wells, etc. have provided similar 

 observations for a few invertebrate species but on the whole the 

 impetus of modern behavioural observations has been towards 

 elucidation of vertebrate systems. 



The life of many invertebrates may seem simple at first glance 

 but as the analysis by Wells and co-workers of the behaviour of 

 Arenicola shows, many complex processes are carried out. No one 

 has as yet subjected Lumbricus or any other oligochaete to such 

 intensive investigation but none the less a number of facts can be 

 reviewed here. 



Earthworms and other oligochaetes tend to be rather secretive 

 animals, nocturnal in habit and easily irritated into hasty removal. 

 As is the case with many other characteristics of the oligochaetes 

 most of our knowledge is confined to the earthworm species. A 

 few behavioural facts are known with regard to Tiibifex^ but these 

 are dealt with elsewhere (Chapter VII on respiration). 



The behaviour of earthworms is influenced, as is that of any 

 other animal, by the changing conditions of the environment 

 which surrounds it. The soil in which earthworms live may seem a 

 fairly rigid and unchanging medium to inhabit, but even 

 here such properties as the acidity of the substrate, the water 

 content, food content, leaf cover and even gas concentrations may 

 have an effect upon the activity and behaviour of earthworms. Most 

 of these factors, and the various changes they undergo, will be 

 detected by the earthworm through the medium of the sense organs. 

 But as we shall see information regarding these sense organs is at 

 present rather scanty. The morphological and anatomical 



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