208 



ARACHNIDS, CENTIPEDES, AND MILLIPEDES— ARTHROPODS 



the bathtub some morning where they ventured and were unable to 

 climb the slick sides to get out. They seem to make no attempt to 

 bite people and they destroy many household insect pests. For this 

 reason they are beneficial and many people will not destroy them when 

 they are found. 





<■%; 



N: 



X 



Courtesy Southwestern Biological Supply Co. 

 Fig. 14.7. Centipede. Dorsal and ventral views. 



Class — Diplopoda 



The millipedes or thousand-legged worms have so many legs that 

 it would seem very difficult to move them all in a coordinated manner, 

 but they manage very nicely. Like the centipedes, the body is divided 

 into segments, but there are two pairs of legs per segment rather than 

 one. Since one pair of appendages is the usual maximum among the 

 arthropods, this condition would be hard to explain but for a study of 



