Aug. i, 1921 
Biological Study of Red Date-Palm Scale 663 
June of 1920. By the latter part of June the fruit steins of the current 
year were well infested. 
Of the infestations on the roots only the so-called superficial roots have 
been observed by the writer to be infested (PL 129, 130). These short, 
fleshy, gnarled roots, forming above ground, at the base of the bole, are 
usually under decaying leaf bases and frequently, on old palms, carry a 
relatively light infestation. They are often so concealed as to be entirely 
protected. Attention was drawn to an infestation below the ground 
surface on the bole of a young palm planted in a commercial grove, but 
on examination it proved to be only a case in which an infested offshoot 
had been set out and planted deeper than normal, thus burying some of 
the scale infestation. It has been reported that the scale has been found 
on the main roots of the palms planted in a very heavy soil at Heber, 
Calif., which cracked open after each irrigation and left the roots more or 
less exposed, but no roots have been observed to be infested in the usual 
sandy soils. 
Some scales may be found in the pinnae of the leaves for a distance of 
from 2 to 6 feet out from the trunk at all seasons of the year, but the 
quantity is usually negligible. They undoubtedly get out there during 
the migratory periods and by the natural pushing out of the growing 
leaves, but usually they are almost completely controlled by the heat of 
summer. In some cases scales will persist under the sand deposited in 
the pinnae and will reproduce, but in most instances this infestation has 
been almost negligible after a few hot, dry days. The greatest number 
are found out on the leaves from the latter part of April until the latter 
part of June, though they occasionally appear again in September and 
October during the so-called fall migratory period. The infestations in 
the leaf pinnae almost always cause brown pittings on the underside of 
the pinnae, and these markings are often used to determine whether a 
tree is infested or not when it can not be cut into. By July only a few 
living insects are found in the leaf pinnae. 
Certain varieties of palms show heavier infestations than others. The 
following generally develop heavy infestations: Horra, Tazizaoot, Rhars, 
and Rohm Gazal. Palms vary greatly in the tightness of their leaf fiber 
and bases, but this does not explain the variation in susceptibility to scale 
attack, as the variety Horra has a relatively tight fiber, but is possibly 
the most severely attacked. 
SEASONAL HISTORY 
The insect has been found in all stages of development at all seasons of 
the year. This would indicate a continual reproduction and overlapping 
of generations. Though possibly the greater number of active larvce 
were observed from March to December, even in January the scale was 
in all stages of development. In January, however, the mortality among 
