CENTIPEDES 45 



General behaviour 



Centipedes are nocturnal creatures and lack an impervious cuti- 

 cular wax-layer (Cloudsley-Thompson, 1954). Their locomotion 

 has long fascinated biologists, but only recently has its mechanics 

 been analysed in detail by means of high-speed photography, 

 showing it to be of evolutionary and functional significance. Ray 

 Lankester, who studied this matter in 1889, reached the conclusion 

 that if the animals had to settle the question themselves they would 

 not get on at all! He ended a letter to Nature with the following 

 well-known rhyme: 



A centipede was happy quite 



Until a toad in fun 



Said, Tray which leg moves after which?'. 



This raised her doubts to such a pitch, 



She fell exhausted in the ditch, 



Not knowing how to run. 



However, Manton (1952, 1953) has recently shown that the 

 long Geophilomorpha have become specialised in the ability to 

 choose and vary their footholds so that they may or may not show 

 a regular repetition of the locomotory pattern all along the body. 

 At the same time they are adapted to burrowing 'by the earthworm- 

 like method of becoming **fat", the active pressing on the soil being 

 done by longitudinal contraction and widening of a segment'. 

 The legs serve as anchoring points, like the chetae of the worm, 

 and when used for walking execute large angles of swing to com- 

 pensate for their shortness. An increase in burrowing capacity is 

 correlated with the presence of large numbers of leg-bearing seg- 

 ments and the burrowing habit explains many of the morpho- 

 logical characters of these animals. The head end of a contracted 

 animal can be thrust forward more rapidly by the contraction of 

 the musculature and telescoping of the segments than by walking. 

 A combination of walking movements in some regions of the body 

 with muscular contractions and expansions in others results in a 

 thrust or a pull being exerted on parts of the body in which the 

 legs are not used. This provides an efficient method of moving 

 across gaps or places where footholds are discontinuous or shifting 

 and must also be of major importance in widening crevices in the 

 soil. 



