28 



BULLETIN 536, U. S. DEPARTMENT OF AGRICULTURE. 



are that, in Hawaii at least, citrus fruits resist fruit-fly infestation of their pulp in pro- 

 portion to the thickness and texture of the rag underlying the rind, the quantity 

 of oil liberated from the oil cells during the process of oviposition, and their ability to 

 develop quickly about the egg cavity the gall-like tissues which so often make of the 

 cavity a prison for the larvae that hatch. The data in Table VIII emphasize the large 

 numbers of eggs deposited in the skin of Citrus spp., and the relatively small number 

 of these that produce larvae able to reach and enter the pulp except in the Chinese 

 oranges, limes, and tangerines. Larvae that succeed in entering the rag from the egg 

 cavity in the rind are unable to reach the pulp except in astonishingly small numbers 

 because of the imperviousness of the rag. It is the persistent attack of successive lots 

 of larvae hatching from different batches of eggs, laid very often in the same puncture, 

 that finally breaks down the barrier between the young larvae and the pulp. If the 

 types of mortality among eggs and larvae in the rind of oranges, grapefruit, and lemons 

 protect those fruits so well under Hawaiian conditions, where the weather is so warm 

 that the adult flies can deposit their eggs every day in the year, they should constitute 

 a valuable factor in control when supplemented by climatic cultural conditions more 

 adverse to the development of C. capitata in other countries. 



Table VIII. — Infestation of citrus by the Mediterranean fruit fly . 









Eggs, appear- 



Larva?. 



Fruit. 





ance. 



Alive. 



Dead. 





Empty. 



Not 

 empty. 



Nor- 

 mal. 



Abnor- 

 mal. 



In 

 punc- 

 ture. 



In rag. 



In 

 pulp. 



In . 

 punc- 

 ture. 



1 



Chinese orange: 





 

 

 

 

 

 

 1 

 

 

 

 

 

 

 



10 

 6 



2 

 1 

 1 

 2 

 1 

 1 

 1 

 1 

 1 

 1 

 1 

 4 

 3 

 1 

 1 





 5 

 4 

 6 

 5 

 9 



15 









6 

 4 

 8 

 5 

 9 





1 



2 













3 















4 



9 









4 



4 



5 











6 





26 











7 







19 

 3 





:::::::::::::::: 



8 















9 

















10. . 











1 



6 



11 











6 



12 



15 







12 



11 

 5 









13 



12 













14 













15 

















Lime: 



1 













13 





2 



15 

 34 







L. 





3 











4 

 10 

 21 

 20 

 33 



9 



4 

 30 



1 

 15 





4 



4 











5 ! 1 



53 



33" 



80 



1 

 1 







1 





6 fi 













 3 

 3 







9 





!:::::::::::■: 



2 







11 



















10 



8 

 

 6 

 4 

 9 



5 

 11 

 5 



7 

 5 



1 

 

 2 

 5 



7 



9 

 9 

 5 

 2 

 2 

 7 

 

 

 13 

 9 

 



25 

 12 

 3 

 3 

 6 

 14 





15 









56 



4 

 49 

 3 





11 











12 



61 



27 









6 



7 

 2 

 9 





13 











14 





15 

 44 











15 









17 





16 











17 

















18 





14 









14 



37 

 12 





19 









30 





20 















Grapefruit: 



1 



83 

 369 

 17 

 4 

 42 

 43 



514 



111 



16 









19 

 26 



28 

 4 





2 



"i" 



1 







3 





10 





4 







5 







9 



203 











4 

 13 





6 











45 





