U6 



MERISTIC VARIATION. 



[PART i. 



- '!. in Blattodea, Mantode.-i and Phasmodea 5, in Acridiodea 3, 

 in Locust' xli-a 4, in Grvllmlcn 2 r 3 1 . 



The fa.-t, originally observed by BRISOUT DE BARXEVILLE", 

 that in various sp.-ei.-s of Blattid the number of tarsal joints 

 may \arv from /nr to /',,/// is therefore of considerable importance 

 in a consideration of th.- manner in which these several forms 

 ha\r been evolved from .-ach other. The species in which BRISOUT 

 oh-crved tlii> variation \\.-iv tdi in number and belonged to four 

 genera of Blatt ida-. 



At mv -ii'_ r u' -tion Mr H. H. BRiNDLEY has made an extended 

 investigation of the matter and a preliminary account of the 

 results arrived at was ^ivun in the Introduction (p. 63). It was 

 found that of Blatta americana 25/ of adults have one or 



n 



I-'K,. 11~>. I. Normal five-jointed left tarsus of Blatta americana. II. Eight 

 tarsus of the same having four joints. 



more tarsi 4-jointe<l. In Blatta orientalis these cases amounted 

 to 15/,, , and of li2 B. germanica examined, 16 had one or more 

 4- joint I'd tarsi. 



Tlu- abnormality occurred soniftimos in one leg and sometimes in 

 another, being more frequent in the legs of the second pair than in those 

 "f the tirst, and much more frequent in the third pair than in either. 

 In some specimens legs of the two sides were symmetrically affected, 

 but this was exceptional. Only one specimen has hitherto been met 

 with having all the tarsi 4-jointed. There was a slightly greater 

 frequency in females than in males. 



When the examination of these abnormal tarsi was begun it was 

 supposed that the variation was congenital, but as explained in a note 

 to the Introduction (p. 65) doubt subsequently arose as to this. It is 

 well known th.-it Blattiche like many other Orthoptera have the power 

 of renewing the appendices ;ifter loss, and Mr Brindley found by 

 experiment ilmt when the tarsus of Jjlu/fn orientalis is renewed after 

 mutilation the resulting tarsus is 4-jointed. It was also found that 

 I y.inted tarsi were much more frequent in adults than in the young. 

 The question therefore arises, is the 4-jointed tarsus ever congenital 1 ? 



1 From liiiUNNKK VON WATTKXWYL, Prmlr. eurup. Orthop., 1882. 

 - Ann. fiit. sue. l-'runc?, s. 2, vi. 1848, Bull., p. xix. 



