1923] The Varieties of Monecphora hicincta 91 
the two varieties and show the same relative size differences 
within the group, 2 largest, 5 medium and 3 smaller (including 
X). These size differences are not clean-cut enough to be always 
certain but they are usually discernible in the primary sperma- 
tocytes. 
Applying these facts to taxonomy, we can say that the 
cytology of Monecphora hicincta var. hicincta and var. ignipecta 
corroborates their close relationship. In some insects, as shown 
by the researches of McClung, Robertson and others on the 
grasshoppers the chromosome number is not a function of the 
species or genus but of the family. All species of the Acrididse 
have 23 chromosomes and all species of the Tettigidse have 27. 
A few apparent exceptions have proved to be due to fusion or 
breaking of certain chromosomes. The generic and specific 
differences are expressed in differences in chromosome size and 
arrangement within the given number. The degree of chromo- 
some similarity has been found to correspond directly to the 
nearness of taxonomic relationship. But so far among the 
Cercopidse studied each species has its own specific chromosome 
number so that the identity of number in the two varieties of 
Monecphora hicincta would substantiate their classification as 
varieties of the same species instead of as separate species. 
Philcenus lineatus has 15 as reduced number of chromosomes, 
while Philcenus leucophthahnus {spumarius) has 12; Aphrophora 
parallela has 15 while Aphrophora quadrinotata has 14 and 
Aphrophora spumaria (European form) has 12; Lepyronia 
quadrangular is has 11; Clastoptera ohtusa has 8, while Clastoptera 
proteus has 7; but Monecphora hicincta has 10 and Monecphora 
ignipecta also has 10. The change from one to the other is not 
great enough to involve a visible change in chromosomes. 
In two other species of Cercopidse the cytological study of 
varietal forms has been recorded; Philcenus leucophthahnus 
{spumarius) collected from goldenrod and wild sunflower at 
Woods Hole and the European form, Aphrophora spumaria, 
collected from grass sweepings in a meadow at Eisenach (Boring, 
Biol. Bull. vol. 24.). In neither case were the varieties accurately 
identified and named, but a wide range of color and distinctness 
