CHROMOSOME-GROUPS OF METAPODIUS AND BANASA. 309 



The usual conclusion follows that spermatozoa containing the 

 large idiochromosome produce females and those containing the 

 small one produce males. It is equally clear that the j-chromo- 

 some, though unpaired and hence a heterotropic chromosome in 

 behavior, is not physiologically comparable to an odd or "acces- 

 sory" chromosome of the usual type. 



The numerical relations between Types A and B are interest- 

 ing. Since in maturation the .y- chromosome couples more fre- 

 quently with the small idiochromosome (which is confined to the 

 male) we should expect to find the jr-chromosome in a majority 

 of the males and in a minority of the females; and such is indeed 

 the case in the 12 individuals that have been examined. Of the 

 seven males, five are of Type A and two of Type B--a ratio 

 that happens to be nearly identical with that shown in the 

 coupling. Of the five females on the other hand, only one is of 

 Type A (with three small chromosomes, Fig. I, c\ l while four 

 are of Type B (Fig. I, /"). The number of individuals is of 

 course too small to give an accurate result ; but as far as they 

 go the facts are in conformity with the expectation created by 

 the mode of coupling in the spermatogenesis. 2 



BANASA. 



The remarkable relations observed in Metapodius tenninalis 

 probably give the explanation of those I formerly described in 

 Banasa cak>a, though I am not yet in a position to prove this 

 positively. I have now new material of this genus from individ- 

 uals ranging from New England to Arizona, and comprising both 

 of the more frequent species, B. calva and B. dimidiata? All 



1 This individual differs from all the others in having 22 instead of 2O large chro- 

 mosomes, or 25 in all. I have found a similar variation in the number of larger 

 chromosomes in different individuals of two other species of the genus ( M. femoratus 

 and M, granalosus} as will be described hereafter. These variations appear to have 

 no constant relation to the presence or absence of the ^-chromosome and hence do 

 not affect the questions here under consideration. 



2 Besides the two types of males and females described above we should expect to 

 find a third type in each sex containing two w-chromosomes and two 5-chromosomes. 

 Such forms have not yet come under my observation, and it is possible that gametes 

 containing both these forms of chromosomes are infertile towards each other. 



3 1 am indebted to the well known hemipterist Mr. E. P. Van Duzee, of Buffalo, 

 for the identification of these and many other species. 



