to the effects of potentially harmful materials entering their 

 system). Suffice it to say that if the Medfly cannot be contained 

 within its present bounds, the amount of pesticide application 

 then necessary to prevent fruit injury in California and possibly 

 other states and the amount necessary to fumigate fruit picked 

 from infested areas would vastly exceed the amount presently 

 contemplated for use in aerial bait sprays. 



Why has the infestation spread so rapidly since last June 

 to now cover more than 1000 square miles in 3 California counties? 

 There may be 2 principal reasons. First, the Medfly in California 

 has probably undergone 4- 5 , generations of reproduction and multi- 

 plication since last June. Under ideal conditions, each female 

 can lay as many as 1000 eggs, but under normal field conditions, 

 each probably lays only 400 eggs or so. Thus, even though half of 

 the eggs were to yield males, a single fertile female by the fifth 

 generation could conceivably give rise to more than 300 billion 

 other females. Of course, given natural mortality, only a small 

 percentage of this possible number is actually realized. Still, 

 it has been enough to result in a major outbreak. A second factor 

 contributing to the rapid spread is the dispersal characteristics 

 of the Medfly. Several research studies have shown that Medflies 

 infrequently fly more than 1 mile or so. However, many years of 

 observing fruit fly behavior in nature in several countries have 

 emphatically illustrated to me that under certain weather conditions, 

 the distance of dispersal can be great, exceeding several miles. 

 These conditions are hot, dry days with strong winds. On such 

 days, I have observed large numbers of fruit flies leaving favor- 

 able host trees and dispersing with the wind. If some of the 

 dispersers were to be carried into upper air currents, they could 

 go for a very long distance. It turns out that such weather con- 

 ditions have been frequent in the infested California areas this 

 spring and summer. Thus, there is real danger of flies being 

 carried over the mountains which presently form a barrier between 

 the great agricultural Central Valley of California and the present 

 areas of Medfly infestation. 



Will the Medfly eventually reach Massachusetts? If the current 

 infestation in California cannot be eradicated, the chances are 

 good that at some time in the future, a shipment of California 

 produce, or more likely an individual travelling from California 

 to Massachusetts carrying a sack of infested fruit from a backyard 

 tree, will result in introduction of the fly to our state. Al- 

 though since 1955 the fly has spread by natural dispersal from 

 Costa Rica to northern Guatemala, the chances of its spreading by 

 natural dispersal from California or other states into Massachusetts 

 is extremely remote. 



Can the Medfly survive in Massachusetts? To answer this 



