CHROMOSOME STUDIES 217 



191, after Davis, '08, p. 72). As in Syrbula, there are twenty- 

 three rod-shaped chromosomes. Among these are the usual 

 three large pairs. The sex chromosome does not rank as 10, 

 but as 8 (Dissosteira) or 9 (Chortophaga) . As in Syrbula, 

 there are three very small pairs in Chortophaga; in Dissosteira 

 two of the three are exceedingly small, one (no. 3) being, how- 

 ever, considerably larger, as in Chorthippus, though still worthy 

 of being grouped among the three small pairs. The 4's, 5's, 

 6's, 7's, and in Dissosteira the 8's form a continuously graded 

 series of sizes similar to the conditions in Syrbula. 



4- Acridiinae (Acrididae) 



In this, the fourth subfamily of Acrididae (fig. 192), we again 

 have twenty-three chromosomes. The size relations differ 

 considerably from those of the oedipodines and truxalines, 

 though there are agreements. There are, as usual, two very 

 large pairs, but the third largest (9's) is smaller than in these 

 subfamilies. The sex chromosome ranks 10. There is a con- 

 siderable gap between IO.1; and the 9's, but the 9's, 8's, 7's, 6's, 

 and 5's form a graded series with less differences in size than 

 in the truxalines and oedipodines. The 4's are much smaller 

 than usual, though still noticeably larger than the 3's. We 

 can therefore say that for these three subfamilies of the Acrididae 

 the number of chromosomes is twenty-three {&). 



5. Locustidae and Gryllidae 



V-shaped chromosomes are very common among the Locusti- 

 dae and Gryllidae. The number of chromosomes in Locustidae 

 seems frequently to be thirty-one or thirty-three. In cases 

 where a smaller number occurs, some of the chromosomes are 

 V-shaped, as in Chorthippus. By counting each of these as 

 two chromosomes, the total number becomes thirty-one. This 

 may be seen by comparing figure 193 of Decticus verrucosus 

 (after Buchner, '09, fig. 82) with figure 202 of Steiroxys trilineata 

 (after Davis, '08). If we assume that the two large V's in the 

 latter are twofold, the number in reality is thirty-one. 



