6 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTURE. 



gum seems to be formed from the outer layer, but soon extends into 

 the spongy tissue and entirely surrounds the egg cavity. The number 

 of larvae found in the punctures in September was always large — 

 from 20 to 30 or 40. Larvae were seen closely massed together in the 

 egg cavity, but although appearing perfectly normal they were inac- 

 tive. In such cases death had occurred recently, for later they be- 

 came brown and shriveled. Occasionally one or two would be seen 

 to move slightly. In some cases two or three larvae had made their 

 way out of the egg cavity and penetrated a short distance into the 

 spongy tissue. In no case, however, was the pulp reached. Why the 

 larvae perished within the egg cavity or soft spongy tissue is not 

 definitely accounted for. It appears to be because of lack of air or 

 through the action of some substance in the rind. 



A large majority of the punctures in green oranges were seen to be 

 entirely sealed by gum. The tendency of citrus fruits, or, in fact, any 

 fruit, to exude gum to repair wounds while they are immature, is well 

 known. The condition of the larvae in the egg cavity — simply dying 

 massed together as they hatched, with no evidence of any attempt to 

 migrate — may indicate suffocation. While many larvae occur in a 

 single cavity, and the space is well occupied, death can hardly be 

 accounted for through compression by growth of tissue or gum forma- 

 tion, because some of them, at least, could work their way out of the 

 cavity. In cases where living larvae were found, from 30 to 40 were 

 seen in a single cavity with plenty of opportunity for migration. 



That fruit-fly larvae require considerable air was shown in the case 

 of those that were transferred into a juicy lemon, where the entrance 

 was completely closed by the posterior tip of the bodies of a half 

 dozen or more of the larvae. Numerous instances of the death of 

 full-grown larvae have been noted to take place in the exuding juices 

 of fruit in glass j ars. In peaches and other fruits, also, there are holes 

 in the outer epidermis, made at first through oviposition and later 

 enlarged and serving for the entrance of air. 



Fruit-fly larvae appear to live largely in decayed tissue; that is, the 

 decay induced by them seems to precede the progress of the larvae. 

 It is possible that in green fruit this decay is not so readily induced. 

 And here, again, the organisms of decay may be kept entirely out 

 of the fruit if the entrance to the surface is effectually closed. 



On September 24, 1913, 25 living young larvae that had just hatched 

 were taken from an egg cavity of the greenest orange found infested and 

 placed through a hole in the rind into the pulp of the same orange. 

 In another orange, also very green, a hole was made connecting the 

 egg cavity with the pulp without disturbing the young larvae in the 

 cavity. In both cases openings were left to the surface. When the 

 fruit was examined on October 3, partly grown larvae were found in 

 both of the oranges mentioned. Only a small percentage, however, 



