THE BLACK FLY OF CITRUS. 45 
NATURAL ENEMIES. 
So far no internal parasites of the black fly have been found in the 
Canal Zone or the Republic of Panama, although careful search was 
made for them. 
Several predators on the insect have been found, most of which 
are coccinellids. These are Hyperaspis calderana Gorh. and H. 
albicoUis Gorh.; Scymnus thoradcus For., S. Jiorni Gorh., S. coloratus 
Gorh., and S. adspersulus Gorh.; and Cryptognatha jlaviceps Crotch. 
Of these the last-named species is apparently the most abundant, but 
none of the coccinellid predators seems to occur in sufficient numbers 
to be of any value in controlling the insect. 
The larvae of a lacewing fly (CJirysopa sp.) have occasionally been 
taken feeding on all stages of the black fly. Judging from the number 
of empty skins of their victims (PI. IV, fig. 2) that the larvae carry 
around with them in the " basket" formed by the long upturned hairs 
on the margin of the dorsum, these predators, if they occurred in 
sufficient numbers, would exercise a considerable influence in the 
control of this pest. These chrysopids are in turn preyed upon by 
a hymenopterous parasite, specimens of which have been reared from 
their pupae. 
Several entomophagous fungi have been found to attack the larval 
and pupal instars of Aleurocanthus woglumi. These are Aschersonia 
spp. and Aegerita webberi Fawcett. These were taken on heavily 
infested trees in the Las Sabanas region in November, but were not 
abundant or well scattered enough so that any faith could be placed 
in their efficacy as a means of natural control for the insect. Ex- 
amination, the following April, showed that the fungi had suffered 
severely during the dry season. 
ARTIFICIAL CONTROL. 
Since natural enemies are no factor in the control of Aleurocanthus 
woglumi, artificial control measures, such as spraying with insecti- 
cides, must be used. The successful control of this pest by sprays 
has already been mentioned by Ritchie (33) who used a modified 
" Florida citrus spray." 
Sufficient work on the control of the black fly on a large scale has 
not yet been done in the Canal Zone to warrant any definite conclu- 
sions, but the preliminary control work that has been carried on 
refutes the idea that such radical measures as were of necessity used 
in the eradication of citrus canker are necessary to hold this insect 
in check. 
The logical time to spray in the Canal Zone and adjoining parts of 
the Republic of Panama is in the dry season, as is shown by the 
meteorological data given under " Seasonal history," page 42. Data 
on sprays at this time have not been obtained. 
