Femur and Trochanter in Arthropods. 1~>9 



think, be applied to all those Arthropods which exhibit this 

 fusion of the second and third joints of the thoracic limbs, 

 accompanied by the persistence of a groove constituting a 

 locus minoris resistentue, admirably adapted for ensuring the 

 process of autotomy. 



While following attentively the phenomenon of eedysis, E 

 have been struck by the violent efforts that Phasmids have 

 to make in order to free themselves from their old chitinous 

 envelope. These clumsy Orthoptera, embarrassed by their 

 long legs, do not always succeed in doing so — a failure which 

 is evidently the cause of their subsequent death. At other 

 times they are obliged to make a sacrifice of one or several of 

 their limbs; the latter, always becoming detached at the 

 groove which corresponds to the line of fusion of the femur 

 and trochanter *, remain fixed in the old envelope with which 

 they are shed. 



1 have been able to observe that out of 100 specimens of 

 Rhaphiderus scabrosus which were kept in captivity and 

 protected from all enemies, 9 had perished through being 

 unable to disengage themselves from their old envelope, and 

 that 22 had survived after having sacrificed one or several of 

 their legs (the 69 others accomplished all their ecdyses without 

 mutilations). We see, then, that 31 per cent, of the Phasmids 

 perished or were mutilated through the ecdyses, a figure 

 which I think must sometimes be exceeded. We may judge, 

 therefore, of what must have happened when the disposition 

 which ensures autotomy was non-existent or had not yet 

 acquired the perfection which it exhibits at the present day. 



The efforts which the insect is obliged to make in order to 

 disengage itself may in certain cases last for an entire day, 

 and are repeated eight times at least during its existence |- 

 The violent strains which result therefrom affect especially 

 the region of the trochanter and the upper extremity of the 

 femur. I am led to believe that we must regard this mechan- 

 ical action as one of the principal causes of the fusion of the 

 trochanter and the femur. It is certain that this fusion has 

 not always existed, and that there have been among the 

 ancestral forms belonging to the existing Phasmids insects 

 in which there was a genuine articulation between these two 

 consecutive segments. There has therefore taken place in 



* This mutilation is evidently a form of autotomy, which in this case 

 we might term eruvial (from exuvice, sloughed skin). The regeneration 

 which ensues always produces a tetramerous tarsus. 



f Although 1 have not yet had an opportunity of noting the exact 

 numher of the ecdyses, 1 have nevertheless been able to remark that this 

 number amounts at least to eight, 



