A BIOLOGICAL STUDY OF THE RED DATE-PALM SCALE, 
PHOENICOCOCCUS MARLATTI 
By Arthur D. Borden 1 
Scientific Assistant , Fruit Insect Investigations, Bureau of Entomology , United States 
Department of Agriculture. 
INTRODUCTION 
The present paper gives the results of a study of the biology of the 
red date-palm scale made during monthly field inspections in the Coa¬ 
chella Valley, Calif., during the year 1920. This study was conducted 
with the object of determining the factors in the life history which may 
be of importance in considering control of this pest. No attempt has 
been made to determine the details of the life cycle, such as length of 
instars, variation in length of life cycle, etc., excepting those more 
important points which bear directly on the general study. Most of 
the work was conducted at the Government Gardens at Mecca, Calif., 
as the older trees in these gardens are generally heavily infested with 
scales, but frequent inspections were made of several of the larger com¬ 
mercial plantings to check up the observations. 
DISTRIBUTION 
This scale was discovered in 1890 by Dr. C. L. Marlatt at Washington, 
D. C., on some date palms imported from Algeria, North Africa. In 
1899 Mr. f. D. A. Cockerell, while in Washington, studied the material 
collected by Dr. Marlatt and described the insect as a new genus and 
species ( Phoenicococcus marlatti Ckll.). Several years later Mr. Cockerell 
found small colonies in palms in the gardens at Tempe, Ariz. Since then 
the infestations have increased, and it has been brought in with prac¬ 
tically all of the later introductions of offshoots into California and 
elsewhere. Distribution of these and other infested offshoots has estab¬ 
lished the scale in practically every garden of imported palms. 
There are over 10,000 imported palms in orchard form in the Coachella 
Valley now, and practically all are infested. 
Ihe quarantine act of 1913 2 affecting interstate movement of infested 
palms has restricted the distribution of this insect outside of the v States 
1 I he writer wishes to acknowledge the assistance of Mr. Bruce Drummond and Mr. A. J. Shamblin of 
Indio Calif., who have given freely of their time and practical field experience. In many ways the present 
work has been corroborated by the observations and experiences of these men. 
a [AN] ACT TO REGULATE THE IMPORTATION OF NURSERY STOCK AND OTHER PLANTS AND PLANT PRODUCTS; 
TO ENABLE THE SECRETARY OF AGRICULTURE TO ESTABLISH AND MAINTAIN QUARANTINE DISTRICTS FOR 
plant diseases and insect pests. ... [Approved August 30, 1912, amended March 4, i 9 i 3l and March 4, 
1917. In U. S. Statutes at Barge, v. 37, pt. 1, p. 315-319, 853-854, 1913; v. 39, Pt. 1, p. 1165-1166, 1917. 
Journal of Agricultural Research, 
Washington, D. C. 
yx 
Vol. XXI, No. 9 
Aug. 1, 1921 
Key No. K-98 
(659) 
