THE BLACK FLY OF CITRUS. 7 
E it is assumed that it was introduced into Jamaica within the last 10 
or 12 years, then its spread from there to the places mentioned before 
has indeed been remarkably rapid, and it is merely a matter of a short 
time until it will occur throughout Cuba, the Bahamas, and the 
citrus-growing regions of Central and South America. 
There is perhaps only one way that an insect like Aleurocanthus 
woglumi can be introduced from an infested region to an uninfested, 
suitable, far distant one and become established. This is on a well- 
infested host plant or parts thereof on which the leaves are allowed 
to remain, so packed that the various stages of the insect can con- 
tinue their development throughout the journey, or at least with- 
stand it. This is because there are several checks to its successful 
establishment: First, a high mortality of the individuals, especially 
in the early instars or at molting time, if subjected to adverse con- 
ditions, such as drying out or heavy rains; secondly, the fact that 
parthenogenesis occurs in A. woglumi just as in other white flies 
whose life history has been worked out; and thirdly, the fact that the 
larvaa are not vigorous crawlers and seldom get more than an inch 
away from the eggs from which they hatch. These factors are con- 
sidered at length in a discussion of the life history of this insect. 
When Aleurocanthus woglumi is favorably introduced into a new 
locality, however, there are several ways In which it may spread and 
become thoroughly established in a region. These methods are 
the natural and the artificial. The natural method includes: First, 
the natural flight or migration of the adults from infested to clean 
plants; secondly, the carriage of the adults and possibly larvas by 
winds. The artificial method includes: First, the carrying of infested 
plants from one place to another either in the form of pot or specimen 
plants or in numbers as in the case of nursery stock or as cuttings; 
secondly, the carrying of adults on vehicles, trains, automobiles, or 
the clothes of persons passing or working among infested trees. 
There is no doubt that the black fly has had at least a half dozen 
or more chances of becoming introduced into the Canal Zone through 
the shipment of infested food plants from Jamaica. In the Canal 
Record for July 31, 1912 (6), this statement appears: "Plants and 
shrubs have been received at Ancon from Director Wilder of the 
Botanical Gardens at Honolulu, from the director of Hope Gardens, 
Kingston, Jamaica, and from the Department of Agriculture in 
Washington, D. C." The Record gives a large list of plants, several 
of which have been found to be hosts of the insect, but unfortunately 
no mention is made of the origin of specific plants and the writers 
have been unable to trace any of the food plants mentioned in the list 
to Jamaica origin. The important point is that plants have been 
brought to Ancon from Jamaica as late as 1912 and undoubtedly 
later, and Ancon, Balboa, and Panama seem to be the most heavily 
