December, ’23[ 
armitage: present status of aphycus 
515 
itself it would not again be susceptible to attack that season, the Aphycus 
would largely die out and the new season would begin with as heavy an 
infestation as the previous one. Strictly speaking the Aphycus would 
not entirely die out each season, as it has been found that there is always 
more or less off-stage scale throughout the year on certain of its more 
succulent host plants, sufficient to carry over a small number of Aphycus 
from one season to the next. 
It has been determined that February 15 is the earliest possible date 
at which scale of a size suitable to the attack of Aphycus could be found 
under these conditions. It was thought that if a sufficient number of 
Aphycus could be liberated at this early date, there would be sufficient 
time to secure control through the two or possibly three generations 
which laboratory experiments indicated were possible in the period 
before the beginning of egg laying by the scale. Field work however soon 
demonstrated that the prevailing temperatures at that season of the 
year so retarded the development of the Aphycus, particularly in the 
pupal stage, that it was practically inactive until after reproduction by 
the scale had started. One citrus association expended $50,000 this 
season in an effort to place a sufficient number of parasites in its orchards 
to offset the short period of effective attack. Though they were able 
to liberate between five and ten million Aphycus during the spring 
months, over their properties, they did not succeed in obtaining the 
desired results. Under these conditions it is obvious that in the “even- 
hatch” areas the Aphycus can never, by itself, control the black scale. 
But while this is true, the Aphycus offers other possibilities of value, as 
in the “uneven-hatch” areas. As a body parasite of the third or 
“rubber” stage and the ovipositing adult itself, the Aphycus assists in 
completing a sequence of enemies attacking the black scale, filling a gap 
between the ladybird, Rhizokius ventralis, and Scutellista cyanea. This 
sequence offers a possibility of control under proper handling. 
One of the faults of Scutellista has been that almost always it has 
matured before ovipositicn by the scale has been completed, with the 
result that many eggs have escaped destruction and a heavy infestation 
of scale has followed in spite of an abundance of this parasite. The 
Aphycus materially increases the efficiency of the Scutellista by attack¬ 
ing the ovipositing adult scale and reducing the period of egg laying, 
thus making it possible for the Scutellista to consume all of the eggs 
deposited. That the Aphycus and Scutellista are serially inclined is 
shown by the frequent finding of both attacking one scale. In one 
