flies to suppress reproduction had been estab- 
lished in laboratory studies, pilot field tests 
were conducted by A. H. Baumhover, 
O. H. Graham, and others in the Entomology 
Research Division, U.S, Department of Agri- 
culture. The first sterile male screw-worms 
were released in a 15-square-mile area at 
Sanabel, Fla., at a calculated overflooding 
rate of 4 sterile flies to 1 wild fly, or 100 
sterile flies per square mile per week. The 
insect population was reduced to a low point 
in 3 months. However, eradication was not 
accomplished, unquestionably because of lack 
of complete isolation by the narrow 2-mile 
stretch of water between Sanabel and the 
mainland. 
The next pilot experiment, conducted in 
Curacao in the Netherlands Antilles, was 
eminently successful. This island has an area 
of 170 square miles, with 40 miles of open 
sea isolating it from the nearest land. Re- 
leases of 400 screw-worm flies per square 
mile per week eliminated all infestation in 
goats and other livestock within 9 weeks. The 
Curacao demonstration will long remain a 
Classic in scientific achievement. It was the 
first time man had ever destroyed entirely 
an insect pest population by introducing into 
its natural environment sterile insects of the 
same species in numbers sufficient to negate 
the reproductive potential of the natural 
population. 
In 1958, after the spectacular results ob- 
tained on Curacao, the Animal Disease Eradi- 
cation Division in the U.S, Department of 
Agriculture, in cooperation with the Florida 
Livestock Board, initiated a large-scale pro- 
gram of sterile screw-worm fly releases in 
Florida, The purpose, of course, was toeradi- 
cate the screw-worm. The success of this 
program is well known. I need only add that 
the estimated savings to cattle growers during 
the past 7 years in Florida and other South- 
eastern States, have amounted to $140 million. 
Cost of the program was about $7 million, if 
cost of quarantine operations along the 
Mississippi River to prevent reinfestation is 
excluded, This was a remarkably profitable 
insect-control operation. 
The Florida results quickly aroused the 
interest of Texan and other southwestern 
cattle growers. In 1962, a new screw-worm 
fly-rearing plant was constructed at Mission, 
98 
Tex., in cooperation with the U.S. Depart- 
ment of Agriculture. The new fly-rearing plant, 
to which C, H, Husman, working with the 
Entomology Research and Animal Disease 
Eradication Divisions, contributed so much, 
is an entomological marvel of our times. It 
covers, 76,000 square feet and employs 300 
people. It was built entirely with funds pro- 
vided by the livestock growers and sportsmen 
in the Southwest. In satisfying a production 
quota of 100 million sterile screw-worm flies 
per week, the fly-rearing plant feeds and pro- 
vides for 14,300,000 larvae every 24 hours. 
The plant has the capacity to produce 150 
million flies if the need arises, 
After inception of the program in 1962, the 
occurrence of scattered light infestations of 
screw-worm flies throughout the fly release 
area in the Southwest caused major changes 
in release strategy. Scattered infestations 
during the spring and fall periods suggested 
that some flies had migrated for distances of 
several hundred miles. Tests with marked 
flies demonstrated that screw-worms could 
travel at least 180 miles from the source of 
release. These findings supported the con- 
clusion that the scattered infestations resulted 
from movement of normal flies into Texas 
from Mexico through the barrier in Mexico 
consisting of a zone 100 miles wide in which 
the sterile flies were released. Widening this 
zone to 200 miles and concentrating releases 
along watercourses where cattle and flies 
congregate have contributed substantially to 
the subsequent marked improvement in results. 
During 1962, the year the program in Texas 
was started, 50,779 cases of screw-worm 
infestation were confirmed. In 1963, there 
were only 6,339 cases, Continued releases in 
1964 reduced the number in 12 months to 
only 239, The protection level was estimated 
to be about 75 percent in 1962, Thus, the 
degree of control during 1964 exceeded 99.5 
percent. Livestock owners in the Southwest 
have estimated that the savings resulting 
from this program, which has cost about 
$12 million so far, have been close to $275 
million. We must agree thatin terms of dollars 
saved, this is a highly successful, nonchemical 
means of insect control. 
The principal obstacle to application of the 
sterile male release technique against tropical 
fruit flies is the high population density that 
