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abdominal segment and which function as a springing 

 organ to enable the Insect to take sudden leaps when 

 alarmed or otherwise disturbed. The force necessaiy io 

 generate the leap is obtained partly by the action of 

 special muscles and partly in virtue of the elasticity of the 

 organ itself. In form the springing organ is fork-like 

 (text-fig. 3), and is composed of an unpaired basal piece 



Text-Fig. 4. — I., Compound hair of an Entomohnjn. II., Clavate 

 hair of a Tomocerus. III., Scale of Tomocerus vulgaris. 

 TV., Extremity of middle foot of Isotoma sensibilis, 

 showing three tenent hairs. 



or manubrium (m), carrying at its distal end a pair of 

 arms, which are termed the dentes (d). Each dens 

 terminates in a small claw-like process — the mucro (t.) ; 

 the mucro varies greatly in form among different species, 

 and affords a useful character for the recognition of the 

 latter. In the Achorutidse the springing organ is either 

 greatly reduced in size, as in Poclura, Achorutes, and 



