10 BULLETIN 885, U. S. DEPARTMENT OF AGRICULTURE. 
bility of the insect to climatic conditions that vary considerably 
from those in which it is now known to occur. 
That the spread of this insect in the Ancon-Balboa-Panama, the 
Cristobal-Colon, the Las Sabanas, and Taboga Island regions is 
entirely due to the widespread dissemination of infested food plants 
is not the writers' idea. Doubtless much of the dispersion has been 
due to this method. But there is sufficient evidence that the 
infestation does spread to uninfested hosts through the flight or 
migration of the adults. This has been shown by numerous field- 
inspection trips. The infestation of large trees such as mango, 
sapodilla, lime, and orange in these regions, many of them much 
older than the introduction of woglumi, would show this. 
At Taboga Island the spread is definitely from the village of 
Taboga along the shore line to the east and west and to the south 
following the paths up the steep " backbone" ridge of the island. 
This spread is most probably a question of the flight of the adults, 
and the rate at which it is taking place on coffee plants along the 
creek leading from the village to the south and opposite side of the 
island substantiates this opinion. 
That the adults do fly or migrate is shown by the following facts: 
There is often a decided variation in the number of adults on the 
young growth in the morning and evening inspections of the same 
trees, indicating a migration of the adults either at dusk or in the 
early morning. On the evening of July 29, 1918, Zetek found several 
adults in his house, indicating that the migration takes place at 
dusk; adults have been taken in spider webs 75 to 100 feet away 
from the nearest infested food plant; the migration from an infested 
food plant to a noninfested one has been demonstrated in Panama; 
and finally, the observations at Corozal indicate that a flight of 400 
feet is possible. The first point mentioned is shown by the seasonal 
abundance records for a year, observations on three different lots 
of trees being made three times a day. Adults caught in spider 
webs were commonly observed in a garden next to the board of 
health laboratory during the months of May and June, 1919. Like- 
wise it was found that the adults were flying from heavily infested 
lime trees to young trees of guayabanon (Annona squamosa) and 
guava (Psidiwn guajava) about 60 feet away and set out in nursery 
rows. Various stages of the pest were later found on the guava, 
but the annona here remained free from all stages except the adults. 
In the yard of Ignacio Molino in Panama early in April, owing to 
a heavy infestation of Aleurocanthus woglumi, two orange trees were 
"dehorned," every leaf and green shoot being cut off of them. 
Early in May, nine new shoots were growing from adventitious buds 
and on these were found adults of the black fly and egg spirals. 
A careful survey of all the plants in the yard was made. At a dis- 
