Jan. IS. i9's Citrous Frutts and Mediterranean Fruit Fly 



317 



The data in the tables make it evident that the cause of the mortality 



is not the acidity of the fruit. The figures are of interest in showing 

 that the mortality occurs largely in the rind, either among the eggs in 

 the punctures or among the newly hatched larvae in the egg cavity 

 where they hatch or in the rag beneath. The percentages of mortality 

 occurring among eggs and newly hatched larva? are given in Table IV. 



Table IV. — Mortality of eggs and larva: of Mediterranean f mil fly in the rind 



Kind of fruit. 



Grapefruit 



Lemons 



Linies 



Kusaie limes. . . . 

 Sweet oranges. . . 

 Sour oranges. . . . 

 Shaddock No. i . 

 Shaddock No. 2 . 

 Chinese orange. . 



Total 

 number 

 of forms 

 exam- 

 ined. 



S, 222 



991 

 1,054 



838 

 3.635 



2.357 



J. 155 



303 



>.039 



Mortality in percentages in 

 rind. 



Among 

 eggs. 



90.5 

 76.1 

 43.1 

 47.6 

 19. o 

 71-7 



3-8 

 ■3-5 



3-7 



Among 

 larvae. 



9-3 

 21.0 

 55.6 

 51.8 

 79.0 

 17-3 

 95-3 

 i8. I 

 46.5 



Total. 



99. s 

 97.1 

 98.7 

 99.4 

 98.0 

 S9.0 

 99.1 

 31.6 

 51- » 



MORTALITY AMONG EGGS 



As eggs deposited in such host fruits as the peach and loquat hatch 

 with great certainty, the writers were of the opinion that the oil in the 

 oil cells of the rind was an active agent in killing the eggs in citrous 

 fruits. In puncturing the rind in the process of forming the egg cavity 

 the female is likely to drill through one or several oil cells and the oil 

 thus freed, though not of sufficient quantity to drive the female away, is 

 sufficient in many instances to kill aU or many of the eggs deposited. 

 The data in Table V indicate that there is no question that the oil causes 

 the death of the eggs. Only 163 out of 1,600 eggs treated with oil 

 hatched, as compared with 1,313 out of 1,600 eggs held as a check. The 

 eggs under observation were dissected out of punctures in Cahfomia 

 apples and placed on fresh foliage in moist jars. The treated eggs were 

 not sprayed according to the usual method, but by bending over them a 

 portion of the rind of fresh orange (in the first record) or fresh lemon (in 

 the second and third records) so that the oil from the ruptured cells 

 reached the eggs in that fine raistlike spray familiar to all who have 

 eaten freshly gathered oranges. The much larger number of treated 

 eggs that hatched in the last record is accounted for by the writers by 

 their being fully 20 hours older than those in the second lot when treated. 

 It should be stated that eggs removed from their host do not usually all 

 hatch, as some sustain slight injuries and others may be infertile. See 

 Table V. 



