A Study of the Chromosomes in three Species of 
Pseudococcus. 
Von 
Franz Schräder 
Bryn Mawr College. 
Mit Tafel Y und VI. 
Introduciion. 
In a preliminary paper (’21) I have already giveii a brief survey of 
cytological observations made on Pseudococcus nipae (Order: Homoptera; 
Family: Coccidae), and the present paper is an attempt to give a more 
detailed account of the chromosomal phenomena in that and other members 
of the genus. It is not my purpose to go into detail in regard to several 
much discussed questions which present themselves in the course of the 
Work, but instead to cmphasize only those points which appear to be of 
special interest and importance in the species under discussion. 
Six species of Pseudococcus were examined; but although all of these 
presented the same main cytological features, the study smimered down 
to three species, either because they were most easily obtained or presented 
more favorable cellular conditions. These three species are Pseudococcus 
citri, P. maritimus, and P. nipae. P. citri is perhaps the most common 
species of the genus in greenhouses of eastem United States and was 
always obtainable. P. maritimus has larger cells than the other two 
species; but males could be gotten for only a short period, and although 
meiotic phases are well represented in my preparations, no good spermato- 
gonial stages were obtained. P. nipae was collected without much diffi- 
culty from palms. It has very small cells, but fumishes clear evidence 
in regard to certain phases. 
The raiity of males in species of Pseudococcus has been remarked by 
several entomologists (Mc Gillivray ’21) and my cytological observations 
are only an incidental Step in my endeavor to clear up the conditions of 
sex production in this group. No attempt will be made in the following 
pages to utilize experimental data, but it may be remarked that although 
