THE COMMON COCKROACH 131 



one tries to crush them as they run, by bringing some 

 heavy body down upon them, the blow too often descends, 

 much to the mortification of the would-be slaughterer, 

 not on the insect aimed at, but upon the ground con- 

 siderably in its rear. There is a fussiness and bustle 

 about their movements which is eminently characteristic : 

 it is not merely that much ground is covered in a short 

 time, but also that the legs themselves are moved with 

 remarkable rapidity. You rarely see a cockroach do any- 

 thing but run ; it hardly ever condescends to walk, and 

 for this reason it and its associates are called the "cur- 

 sorial " or running group of the order Orthoptera, while 

 the grasshoppers, our other chief division of the order, 

 which are distinguished by their leaping powers, and 

 could not possibly run, are described as the " saltatorial," 

 or leaping Orthoptera. 



And yet, notwithstanding the speed of which the cock- 

 roach is capable, there is nothing exceptional in the 

 mechanism of the movements, and the slowest crawling 

 insect moves its six legs by precisely the same means, 

 and in precisely the same order, as this agile creature. 

 We may, therefore, take the structure and method of 

 use of a cockroach's legs as typical of all creeping, 

 walking, and running insects; and there is much in 

 them that will well repay a careful and thoughtful 

 examination. Like those of all other insects, and of 

 centipedes, spiders, scorpions, crabs, and lobsters, and 

 many other allied animals, the legs are composed of a 

 series of pieces jointed together in longitudinal order: 

 and each piece is essentially a hollow tube, the hard and 

 stiff walls of which give the limb its unalterable form, 

 while they furnish support inside to the muscles by 

 which it is moved. In some of the above animals addi- 

 tional firmness and strength is imparted to this hard 



