14 BULLETIN 885, U. S. DEPARTMENT OF AGRICULTURE. 
These 2 tables are characteristic of 30 that were kept on lime 
trees. The field observations at Ancon, Balboa, and Cristobal indi- 
cate that an infestation of Aleurocanthus woglumi on this host, while 
persistent and oftentimes heavy, does not progress with the rapidity 
that it does on such hosts as grapefruit, orange, and tangerine. 
Further discussion of this point is given under " Injury," page 18.^H 
In this connection see Plates I, II, and III. 
Many of the trees along the roads and on the lawns in Ancon 
came to the Canal Zone in 1916 as nursery stock from Aguadulce, 
Republic of Panama, and all those trees are more or less uniformly 
infested, indicating either that they were all infested at the time that 
they were set out, or that they became so shortly thereafter through 
eggs laid on them by migrating adults. It has recently (Sept. 15, 
1919) been ascertained, however, through a letter accompanied by 
specimens, that Aleurocanthus woglumi is firmly established at Agua- 
dulce. This would indicate that the trees were infested at the time ^ 
they were set out, and if the rate at which the infestation on the 
trees is progressing is any criterion by which to judge the time that 
woglumi has been present in the Canal Zone, it is safe to say that it 
was first introduced there not later than 1912, for these lime trees 
must yet, after three years, be regarded as only moderately infested. 
On this basis and assuming that it came to the Canal Zone during or 
before 1912, then it has been in Jamaica 15 or more years or at least 
since before 1910. 
In Jamaica and Cuba the insect's spread has paralleled that in the 
Canal Zone. In the former place after being introduced into the 
vicinity of Kingston it spread around this locality by both natural 
and artificial means, but its dispersion to the more distant parts of 
the island was unquestionably by means of infested food plants^ fc 
Once it was introduced into a new locality its spread there was by 
both natural and artificial means. In Cuba it was first introduced 
into the Guantanamo region on infested plants from Jamaica and its 
spread took place by both natural and artificial means. From Guan- 
tanamo it was carried to Havana on infested plants, where its spread 
was again by natural and artificial means. Whether or not the in- 
festation in the region of Santiago de la Cuba is a separate introduc- 
tion of infested plants from Jamaica or whether it is traceable to 
infested plants from the Guantanamo region is not known. 
FOOD PLANTS. , 
The food plants of the black fly fall under the three following 
heads: (1) The favorite or preferred food plants, i. e., those that be- 
come heavily infested with the insect and on which complete develop- 
ment from egg to adult takes place; (2) the occasional food plants, 
i. e., those on which complete development of the insect can and does 
