BIOLOGY OF THE PAPAYA FRUIT FLY. 9 



by Mr. Edward Simmonds, and is known as No. 28533. These oblong 

 fruits are much more immune to the attacks of the flies, due largely 

 to the fact that the female flies are unable to reach through the flesh 

 of the fruit with their ovipositors and lay their eggs. In fact, in some 

 places they were found practically free from infestation and are 

 considered immune by the growers. An examination of about 300 

 fruits of all kinds on the Florida Keys, by A. L. Swanson, an in- 

 spector of the State Plant Board of Florida, showed 90 per cent of 

 infestation in the small round fruits as compared to no infestation 

 in the large oblong fruits. This latter fact has not held good, how- 

 ever, in investigations by the writer. Several hundred fruits ex- 

 amined both on the keys and in many places on the mainland showed 

 about 88 per cent of the round or oval fruits infested and about 15 

 per cent of the oblong fruits infested. In wild fruits in the ham- 

 mocks the infestation is close to 100 per cent. No papayas grown in 

 the State are entirely immune from the attack of the flies. 



ENEMIES. 



Only two natural enemies have been noted on this insect, one the 

 jumping spiders and the other the small red ants which sometimes 

 prey upon the larvae. The large black jumping spiders conceal them- 

 selves between the fruits on the tree and are then able to catch the 

 flies when they alight near them. Doubtless they destroy many in 

 this way. On a few occasions ants have been observed attacking 

 the maggots in a fruit which had fallen to the ground. They enter 

 through the exit hole of the first maggot to escape and can then 

 destroy the remaining larvse in the fruit. They represent a neg- 

 ligible factor, however, in the control of the pest. 



Six hundred pupse dug from the soil under the trees and bred out 

 in jars failed to produce a single parasite. The insect is well pro- 

 tected from the attack of parasites through nearly the entire period 

 of its life. 



CONTROL MEASURES. 



The most effective way of preventing injury from this pest is by 

 bagging the trees or fruits. Either cheesecloth or mosquito netting 

 can bft tied over the trees or around the individual fruits, and the 

 flies will not try to sting the fruits through it. However, this plan 

 is hardly practicable on a large scale, since it requires considerable 

 work and expense and, in many cases, changing the bags as the fruits 

 grow larger. 



The adults are readily killed by feeding them a poisoned sirup, 

 the best results being obtained by using sodium arsenite or potassium 

 arsenate dissolved in brown sugar sirup. When given this sirup 

 the adult flies die very soon after feeding, and they eat it as readily 



