268 



THE UNIVERSITY SCIENCE BULLETIN. 



Chromosomes of Nomotettix. 

 Myrtle F. Rayburn. 



In the table for Nomotettix cristatus Scudder, the fii'st six horizontal bars represent 

 the relative lengths of the six pairs of autosomes, and the seventh the percentage that the 

 sex chromosome is of the total sum of the lengths of the autosomes. 



In the relative lengths of chromosomes, the genus Nomotet- 

 tix is more nearly like the genus Acridium than Paratettix or 

 Tettigidea, as shown in particular by the measurements for the 

 fifth and sixth pairs of chromosomes. Compare the relative 

 lengths of these, 20.54 to 27.75, for the spermatogonia of 

 Nomotettix, with those for the same chromosomes in Acridium, 

 the genus to which Nomotettix is most nearly related taxonom- 

 ically. Again, compare the relative lengths of the smallest and 

 intermediate pairs with those of Acridium. It will be seen that 

 there is not so very much difference. The smallest pairs, whose 

 lengths are 9.82 and 11.83, compare very similar to the lengths 

 10.48 and 11.49 for Acridium granelatus or 11 and 11.06 for 

 A. incurvatus. The intermediate pairs, 14.17 and 15.86, are 

 slightly larger than in Acridium, the species ornatus excepted. 

 These numbers in Acridium are as follows : For granulatus, 

 13.31 and 14.08 ; for incurvatus, 13.4 and 14.3 ; for obscurus, 

 13.3 and 14.1 ; but for ornatus 14.63 and 15.86. 



The difference in length between the longer of the inter- 

 mediate pairs and the shorter of the two longest pairs is about 

 one-half as great as in the species of Acridium. Compare the 

 ratio 15.86 to 20.54 of Nomotettix with 14.08 to 22.48 of A. 

 granulatus, 14.3 to 22.5 of A. incurvatus, 15.86 to 21.47 of A. 

 ornatus and 14.1 to 22.1 of A. ohscw^us. This is one point at 

 which there is a rather marked disagreement between 

 Nomotettix and Acridium. 



In comparing the relative lengths of these chromosomes, as 

 shown by the tables of my text figure, with those of Robertson 

 for Paratettix and Acridium, it may at once be seen that 



