164 
Psyche 
[September 
POSSIBLE POLYPLOIDY IN THE 
HYMENOPTERA 
By Sheldon C. Reed 
Bussey Institution, Harvard University 
The Bresslau-Harnisch lists of animal chromosome num- 
bers (Tab, Biol. 4) include data for the twenty species of 
Hymenoptera whose chromosome numbers were known at 
that time. Records subsequently published give the num- 
bers in two additional species, Habrobracon juglandis and 
Pteronidea ribesii . The total may be summarized in this 
fashion : 
1 species, haploid number U 
8 
u 
8 
1 
3 
5 
a 
a 
“ 16 
“ 12 
3 
“ 16 
1 
“ 2U 
Eighteen of the twenty-two species have chromosome 
numbers of 4 or a multiple of 4 ; whereas only four species 
have different chromosome numbers (9 or 10) . These num- 
bers are representative of seven families out of more than 
one hundred in the Hymenoptera and seem to be a random 
sample of what may be expected to be the situation in the 
other species whose chromosome numbers are yet unknown. 
Though the number of species which have been investigated 
is very small, the idea suggests itself that these chromo- 
some numbers may be a result of polyploidy such as is 
known to occur in plants. 
