1961] 
Insect Control Programs 
97 
received good publicity in the press and on television and radio, and 
most tropical fish producers were able to cover their ponds, while 
paint and plastic testing laboratories could spread plastic sheeting 
over their test plates. Housewives were advised to withhold wash 
from clotheslines, and automobile owners to cover or be prepared to 
wash their cars. Some damage was noted on cars with lacquer finishes, 
but not on those with enamel, and the spotting proved to have been 
caused by malathion. Some loss of tropical fish was also reported, but 
not in ponds with deep enough water. Reported losses of birds, 
mammals and beneficial insects were not confirmed upon investigation. 
One C-84 twin-engine aircraft crashed at Boca Raton while ferrying 
materials, killing a crew of five men. 
Side benefits from the spray included control or depression of insect 
pests such as houseflies, mosquitoes and the papaya fruit fly during 
the period of application. 
THE SCREW WORM 
Introduction 
The screwworm is the maggot (larva) of a large fly ( Callitroga 
hominivorax , plus at least one other species occurring outside the area 
concerned). The maggot lives in the flesh of warm-blooded animals 
and gets its name from its fancied resemblance to a wood screw. All 
sorts of mammals are attacked, but from the human standpoint in this 
country, the damage it inflicts on cattle has been most important. The 
screwworm has a year-round range in the American tropics and Sub- 
tropics, from Texas and other border states south to Argentina. Each 
summer, screwworm flies migrate northward to spread the infestation 
into the midwestern states, and infestations are known to have been 
introduced into Illinois, Iowa, New Jersey, South Dakota and other 
northern states in livestock shipments carrying the pest. Each year 
up to 1933, winter cold killed the infestation back to the southern 
parts of the border states and to Mexico, where the winter weather is 
mild enough to permit permanence of the fly population. 
In the summer of 1933, screwworms appeared for the first time in 
the southeastern United States, probably shipped in infested south- 
western livestock, and before they could be controlled they had spread 
into peninsular Florida. Here they found the climate mild enough to 
support a year-round population, and thus a permanent infestation 
became established in the Southeast. Each summer this infestation 
spread outward from Florida into additional southeastern states, and 
each winter it died back to Florida and the warmer parts of Georgia 
and Alabama. During 1935-1937, the affected states in cooperation 
