238 Regeiieration of Tarsus &c. in Orthoptera saltatoria. 



regeneration occurs in the second case, a jointless stump is 

 formed hardly 2 or 3 millim. in length. The facts described 

 explain themselves completely. 



On the other hand, however, it may seem inexplicable that 

 exuvial self-mutilation should show itself in the case of limbs 

 which it appears h 'priori ought to experience no difficulty 

 in withdrawing from their old chitinous covering, such 

 limbs being of sufficiently restricted dimensions. 1 should, 

 however, call attention to the fact that among the Arthropoda 

 when moulting there is not a single "appendage (leg, antenna, 

 palp), however modest its dimensions may be, in which there 

 may not at the particular moment happen to be accidental 

 adhesions between the new chitinous covering and the old. 

 The Arthropod which cannot when moulting overcome these 

 difficulties is infallibly doomed to die. This furnishes the 

 explanation why in moulting Arthropoda there ought to be 

 but very.few appendages in which one cannot find traces of 

 more or less marked exuvial self-mutilation *, either complete 

 or partial, and at the same time of regenerative power. It 

 may even sometimes be possible to discover regeneration in 

 certain parts belonging to limbs specially modified for quite 

 particular functions. This is the case with the tarsi of the 

 preying-legs of the Mantidse and those of the digging-legs in 

 the mole-crickets. Further mutilation of these limbs would end 

 in death either indirectly or after a brief delay and by bleeding. 

 II. — In the Orthoptera saltatoria regeneration of the tarsi 

 in the three pairs of limbs takes place with ease ; this is to be 

 expected, seeing that the tarsi are frequently damaged as a 

 result of the struggles made by the insect to free itself when 

 moulting. It is particularly well marked in the elongated 

 tarsi of the jumping-legs. Regeneration here takes place even 

 after artificial cuts removing the tarsus, and even a little 

 piece of the terminal portion of the tibia, which is reproduced 

 as well. The presence of the regenerative power in the last- 

 mentioned region is easily explained when it is taken into 

 consideration that its muscular fibres are often damaged when 

 the tarsus is torn off either during moulting or, more rarely, 

 by the unsuccessful attack of some natural enemy. 



III. — In Phylloptera laurifolia and Conocephalus differens 

 regeneration gives a tetramerous tarsus (tetramery is the rule 



never reaches the length of the corresponding one that remains in place, 

 and it is often incapable of rendering any real service. It is probably 

 this slowness of growth that led Graber to conclude too hastily that 

 regeneration of the tarsus did not take place. 



* The greater perfection of exuvial self-mutilation is properly directed 

 to the difficulties which appendages, owing to their shape or size, expe- 

 rience in disengaging themselves from their old chitinous coat. 



