64 
Psyche 
[March 
tic species, . . there is no ‘mechanical’ barrier to the establishment 
of any type of polyploidy in such forms and various forms of aneu- 
ploidy, due to irregular reduplication of some chromosome elements, 
must be expected to occur.” 
ADDENDUM 
Since this paper went to press we have obtained the following ad- 
ditional information concerning Pycnoscelus. Dr. Barbara Stay gave 
us several specimens of P. s.urinamensis which she collected in Queen 
Elizabeth Park, Lake Edward, Uganda, Africa. A colony has been 
established and there are 54 chromosomes in this clone (20 cells in 
2 nymphs were examined). The number of chromosomes is the 
same as that found in the females from Jamaica and Panama. The 
African females also resemble the Jamaican and Panamanian forms 
in size, coloration, and wing length. 
A colony of P. surinamensis was established from 2 adult females 
collected in Puraquequara, Rio Negro, Amazonas, Brazil. This 
clone has 39 chromosomes (40 cells from 4 female nymphs were 
examined) . 
We also crossed 16 P. surinamensis females from Bogor, Indo- 
nesia (37 chromosomes) with males of P. indicus from Hawaii (35 
or 37 chromosomes). All the females had sperm in their sperma- 
thecae when they were examined after producing young. Two hun- 
dred and seven females were reared and these had 37 chromosomes 
like their mothers (50 cells from 5 nymphs which originated from 
3 different females, were examined). Only one male was produced. 
However, this male had 35 chromosomes and one would expect it 
to have had 36 if it originated parthenogenetically. It is possible 
that the male was P. indicus which accidentally got into the con- 
tainer of nymphs being reared. 
SUMMARY 
The bisexual species P. indicus, from which the parthenogenetic 
species P. surinamensis apparently arose, has chromosomal polymor- 
phism and is 2n ( cT ) — 35 and 37, and 2n ($) = 36 and 38. 
Parthenogenetic Pycnoscelus surinamensis is cytogenetically polymor- 
phic, probably arose polyphyletically, and may be aneuploid or poly- 
ploid. The modal numbers of chromosomes of P. surinamensis are 
34 (Brazil^ Australia, Thailand), 35 (Thailand), 37 (Indonesia), 
39 (Brazil), 53 (U.S., Brazil), and 54 (Panama, Jamaica, Africa). 
