CHROMOSOMES OF 
THE PYCNOSCELUS INDICUS AND 
P. SURINAMENSIS COMPLEX 
(BLATTARIA: BLABERIDAE: PYCNOSCELINAE)* 
By Louis M. Roth and Samuel H. Cohen 
Pioneering Research Laboratory 
U. S. Army Natick Laboratories 
Natick, Massachusetts 01760 
The chromosome numbers of both parthenogenetic and bisexual 
forms of Pycnoscelus surinamensis (L. ) have been reported to be 
38 ($) and 37 ( c? ) by Matthey ( 1945, specimens from the botanical 
garden and crocodile house in Berlin; 1948, specimens from Kuala 
Lumpur, Malaya), and 36 (9 parthenogenetic) by Suomalainen 
(1945, specimens from the botanical garden and crocodile house in 
Berlin). Reproductive behavior (Roth and Willis, 1968), and cross- 
ing experiments (Roth, 1967) have shown that the parthenogenetic 
and bisexual “strains” are physiologically sexually isolated from one 
another and Roth (1967) applied the name Pycnoscelus indicus (F.) 
to the bisexual taxon from which the parthenogenetic form (P . sur- 
inamensis) apparently arose. The specimens used in the 1967 study 
originated from Florida, Hawaii, Australia, and Indonesia. In this 
paper we report the results of a study of the numbers and morphology 
of the chromosomes of P. indicus , and clones of P. surinamensis 
from different geographical areas. Pycnoscelus surinamensis is cos- 
mopolitan, whereas P. indicus appears to be restricted mainly to the 
Indo-Malayan region. 
MATERIALS AND METHODS 
The Pycnoscelus which were cultured in the laboratory originated 
from Florida, Jamaica, Panama, Brazil, Hawaii, Australia, Indo- 
nesia, and Thailand (see acknowledgements). It is possible that 
certain cytogenetic forms have been eliminated in those cultures of 
Pycnoscelus (e.g., from Florida and Australia) which have been kept 
for years in the laboratory. However, the specimens from Jamaica, 
Panama, Brazil, and Thailand were for the most part F* or F 2 
offspring from the original material collected. 
The methods used in preparing slides of mitotic figures were 
modifications of Tjio and Whang (1962) and Wolstenholme 
* Manuscript received by the editor April 8, 1968 
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