438 SNODGRASS 



posterior tibiae continuously dusky, differing thus from the Charles 

 and agreeing with the Chatham and Hood forms. 



From Barrington Island. 



Sphingonotus tetranesiotis hoodensis. — Head and thorax uniform 

 reddish-brown ; tegminal maculations confined to lateral sloping sur- 

 faces ; lower three fourths of hind tibia continuously dusky ; a longi- 

 tudinal dark band on lower surface of hind femur as in charlesensis . 



Closely resembles the Charles race in all except the dusky color on 

 hind tibia, agreeing thus with the Barrington form, but differs from 

 the latter in the longitudinal dark band on lower surface of hind 

 femur. 



From Hood Island. 



Sphingonotus tetranesiotis indefatigabilensis. — General coloration 

 similar to that of the Charles form, but more reddish ; maculations of 

 tegmina not forming continuous cross-bands ; no longitudinal band 

 on ventral surface of metathoracic femur. 



From Indefatigable Island. 



RELATIONSHIPS OF THE SphingOtlOtuS RACES. 



The two species of Sphingonotus, as characterized above in their 

 varieties, differ from each other as follows : the trinesiotic forms have 

 pale longitudinal bands on the angles of the pronotum, and the genas 

 differ in color from the rest of the head ; the tetranesiotic forms have 

 no markings on either the head or the thorax, and the genae are uni- 

 form in color with the rest of the head. 



If we compare the distribution of the races of Sphingonotus with 

 that of the Galapagos races of Schistocerca^ little similarity will be 

 found between the two cases. They agree only in this : that all the 

 varieties in each genus can be referred to two species, and that one 

 race of one species lives on Chatham Island and one race of the other 

 on Charles. The charactei^s of the varieties themselves give no 

 evidence in either species, of any one's being the ancestor of the others. 

 On the other hand, there is nothing to oppose the supposition that 

 Chatham and Charles Islands were respectively the original homes of 

 S. trinesiotis and S. tetranesiotis. It is easy to imagine how the 

 races on the other islands might have descended from forms on Chat- 

 ham and Charles similar to those now found there. The geologic and 

 climatic characters of the various islands point to Chatham and Charles 

 as being the oldest inhabitable parts of the archipelago. Hence, we 

 may suppose that these two Islands were the first to be populated by 

 representatives of the genus. Here they could have become dif- 



