Jan. IS. 19.5 Citrous Fruits and Mediterranean Fruit Fly 315 



cainilo). In either case the frviit is rendered worthless by the developing 

 larvae before it is ripe. When the larvte become well grown, they leave 

 the fruit (PI. XL) either before or after it has fallen and enter the 

 ground or other protected places and transform to the pupal stage, from 

 which the adult later emerges. In Hawaii the Mediterranean fruit fly 

 requires in passing from the egg to the adult stage from i^l4 days in sum- 

 mer to about 47 days during the coldest winter weather. In this paper 

 the words "puncture" and "egg cavity" are often used synonymously. 



PROPORTION OK EGG PUNCTURES CONTAINING EGGS 



The data in Table I show that many of the punctures in the rind made 

 by the female contain no eggs. In one of the most favored host fruits, 

 the peach, practically all the punctures made contain eggs. Of 534 punc- 

 tures made in 112 peaches but 13 were empty. The rind of lemon con- 

 tains a much higher percentage of empty punctures than that of any of 

 the other citrous fruits in Hawaii, except the Kusaie lime (Citrus limettd). 

 In the 50 fruits examined 380 empty punctures were found, as compared 

 with 185 with eggs. Practically all punctures in Chinese oranges contain 

 eggs. (See Table I.) In the 85 fruits examined only 1 puncture out of 

 116 was empty. Grapefnut, or pomelos, shaddocks, and sour oranges 

 seem to be preferred for oviposition to the ordinary budded or seedling 

 oranges. It has been noted that adult fruit flies, especially the males, 

 congregate in large numbers on citrous trees, and in the laboratory both 

 sexes are quickly attracted to pieces of cut rind of citrous fruits. They 

 seem to take pleasure in feeding upon the oils and other substances con- 

 tained in the broken cells, and it is possible that in the field their liking 

 for juices made available by the process of forming the egg cavity is so 

 great that the females discontinue ovipositing and begin feeding. The 

 large percentage of empty punctures in lemons and Kusaie limes, in par- 

 ticular, can not be ascribed to a lack of ripeness, as in practically all in- 

 stances the fruits examined were fully grown and a large percentage were 

 colored and overripe. 



MORTALITY OF EGGS AND I.ARV^ 



Although many punctures in citrous fruits may be empty, others con- 

 tain a sufficient number of eggs to infest badly a fruit not so well 

 equipped by nature to withstand attack. Out of 13 punctures in one 

 grapefruit 9 contained 76, 153, 32, 25, 18, 8, 46, 113, and 9 eggs, respec- 

 tively. While this is a larger number of eggs than is usually found in a 

 like number of punctures, it is sufficient when supplemented by the data 

 from other citrous fruits to arouse interest in finding a reason why, with 

 so many eggs deposited in citrous fruits, so very few flies succeed in reaching 

 maturity. (See Table I.) Thirty-nine oranges, cither yellow or orange in 

 color, picked from the trees on September 13, 1913, and containing an 

 average of 32 punctures, with a maximum of 108 and a minimum of 7 



