Jan. 15. 1915 Citrous Fruits and Mediterranean Fruit Fly 



321 



down between the sections of the fruit, but seem to be lacking in strength 

 to penetrate the skin after they have reached it. There apparently is 

 nothing in the rag itself as a food to cause the death of the larvae, as larvae 

 can attain full growth when feeding on the rag of certain shaddocks. 

 Whether larvae die or not seems dependent upon the degree of toughness 

 of the rag, and the closeness with which the rag adheres to the skin 

 covering the pulp. The toughest rag found was that of sweet oranges 

 still hanging on the tree in March in a much overripe condition. These 

 fruits had begun to be pithy at the stem end, and the rind, which was 

 more or less russeted, had begun to wither and yielded no oil when sharply 

 bent. These fruits were very much like the over- 

 ripe, badly russeted seedling oranges frequently 

 found on trees in Florida during April and May as 

 "leftovers" from the winter crop. In the 20 

 fruits examined, containing an average of 7 punc- 

 tures to the fruit, no larva was able to penetrate 

 the rag. The coarsest rag or that with the loosest 

 texture is that found in certain large shaddocks 

 growing in Hilo, Hawaii (PI. XLI). These fruits 

 were much overripe when gathered from the tree 

 in March. An examination of 14 of these fruit- 

 showed that out of 245 larvae, mostly in the third 

 instar, present in the rag and pulp, 152 were alive 

 in the rag, 55 alive in the pulp, and only 38 dead, all 

 in the rag. Fourteen other shaddocks, apparently 

 in the same state of ripeness but growing on 

 another tree and so very much undersized as to 

 resemble a medium-sized grapefruit, had a very 

 much tougher rag. An examination of these fruits 

 showed that but 5 very young larvae out of 701 

 found in the rag were alive and that no larvae had 

 succeeded in penetrating the pulp. The data in 

 Table I show that in the grapefruit, lemons, limes, 

 and sweet oranges examined, 326, 15, 424, and 

 1,552 first-instar larvae, respectively, died in their 

 attempt to puncture the rag, as compared with but i first-instar larva 

 found alive in the rag of grapefruit and 17 third-instar larvae found in the 

 pulp of sweet oranges. 



The ordinary sour orange of Hawaii, which is identical wiih that grown 

 in Florida, possesses a loosely attached rind the rag of which is much 

 looser in texture and from the standpoint of imperviousness to the young 

 larvae seems half way between that of the ordinary sweet orange and large 

 well-ripened shaddocks. After the larv-ae have succeeded in passing 

 through the rag of these oranges they work their way between the rag 

 and the skin and finallv enter the pulp, usually at the blossom end. 



"^m 



1 



1 



Fig. 3. — Section of grapefruit 



rind, showing two egg cavi- 

 ties, one in cross section. 

 Drawing made one week 

 after fruit was picked. Note 

 conical elevation about tlie 

 eyg cavities left by the 

 withering of the rind; also 

 the thickened walls of the 

 egg cavity and the single 

 larval channel in the rue- 

 Original. 



