434 SNODGRASS 



from this island the yellow at the angle of the scvitum extends to the 

 posterior border of the scutellum. The yellow has spread over the top 

 of the head so that the general black color is confined to a post-ocvilar 

 stripe between the color of the vertex and the post-genal yellow stripe 

 of the tuelanocera form. Furthermore, this black post-ocular stripe is 

 split longitudinally with yellow. This replacement of the black by the 

 yellow until the latter becomes the ground color and the black appears 

 as markings is characteristic of the whole Duncan race, yet the speci- 

 mens grade imperceptibly from the extreme representing the Hood 

 type into that representing the Charles Island type. 



The sides of the mesothorax and of the metathorax are in all nearly 

 uniform brownish-yellow. The abdomen is brown with black mot- 

 tlings and without pale borders to the segments. The hind femora are 

 generally of a rather faded appearance but possess most of the black 

 tnelanocera femoral markings undiminished in size. The tegmina of 

 nearly all are grayish in color, being noticeably so when a specimen is 

 seen alive flying, and the reticulation is almost everywhere pale. The 

 maculations are as described in the type. The longitudinal veins vary 

 from red to a reddish-brown — a vein-color not present in any of the 

 melanocera forms, being more nearly the vein-color of the literosa 

 varieties. The posterior wings are plain as in the type. 



There can be no doubt that this race is intermediate between the 

 forms from Charles and from Hood and it is evident that the change 

 in color pattern from the Charles type to the Hood type consists of a 

 spreading of the yellow markings of the former over the black ground 

 color until the relationship of the two colors is reversed, and the black 

 appears as markings on a yellowish ground. In addition to this dif- 

 ference of color pattern there is a difference of general tone of color- 

 ation, and of presence and absence of markings on the tegmina. 



Length of tegmina of viale, 42, 44, 44, 43, 44, 42, 42, 41, 43, 41, 

 41, 42 = 42.3 mm. ; oi female, 54, 50, 53, 54, 54, 53, 47, 52, 54, 54, 



56, 55 = 53 i^m- 



In general the Chatham Island form presents fewer variations in the 

 direction of the Duncan variety than does the Hood Island form, and 

 such variations as are in that direction do not go nearly so far as do 

 some of the variations found amongst the Hood specimens, but tend 

 rather to connect the Chatham race with the t3'pical specimens from 

 the latter island. The Hood race, therefore, is intermediate between 

 the Duncan race and the Chatham race. The relationship holds spe- 

 cially with regard to size, the Hood form being the largest of all the 

 literosa varieties. 



