THE BLACK FLY OF CITRUS. 47 
POSSIBILITY OF THE INSECT BEING INTRODUCED INTO THE UNITED 
STATES AND FACTORS INFLUENCING ITS ESTABLISHMENT HERE. 
The presence of the black fly in Cuba, in the region of Habana, 
and on the island of New Providence is doubtless a menace from the 
point of view of the possibility of its introduction into Florida and 
becoming established there. Theoretically there are several ways 
that such introduction may take place. The first of these methods 
is on nursery stock infested with any or all stages; the second is on 
infested individual plants or parts of plants infested with eggs or 
pupae brought in by travelers from Cuba or Nassau; the third, by 
eggs of the insect laid on fruits; the fourth, by infested parts of 
plants mixed in shipments of fruits; and the fifth, by adults brought 
in on freight cars from Cuba via the railroad ferry plying between 
Habana and Key West. In the case of insects like the Aleurodid^e 
the stages that are introduced and the conditions under which they 
are introduced and to which they are subjected after introduction 
have a decided bearing on whether or not they will be able to main- 
tain themselves and become established. 
The first and second of these methods are the ones by which the 
insect is most likely to gain entrance into the United States and 
become established here, for the high mortality that takes place, 
especially in the early stages, means that plants or parts thereof 
brought into a new locality must be well infested if the insect is to 
establish itself. This is the way the insect became introduced into 
Jamaica, Cuba, the Canal Zone and Panama, Costa Rica, and New 
Providence. 
Heavily infested parts of plants will have to be brought in fresh 
if the insect is to become introduced and established in this manner. 
The following experiments on the effects of the drying of the pupa 
-cases of the insect on the emergence of the adults show what may 
be expected from parts of infested plants that have begun to dry 
out. These will also apply to the possibility of the insect becoming 
introduced on parts of plants mixed in shipments of fruits. 
EXPERIMENT NO. 1. 
Started May 10 — Pupal stage. 
Number of leaves — Seven leaves used in this experiment. These were kept 
in a 5|-inch covered petri dish. (Lime leaves.) 
Number of pupse — 100 males and 200 females. Adults had been previously 
emerging from same colonies. 
Hemarks: 
May 11 — Two males and two females emerged . 
May 12 — Six males and eight females emerged. 
May 13 — Three males and six females emerged. 
May 14 — Two males and three females emerged. 
May 15 — Five maler and six females emerged. Individuals having 
trouble getting out of pupa cases, due to dryness. 
