lau. IS. 1915 Citrous fruits and Mediterranean Fruit Fly 323 



It is evident, therefore, that larvae hatching from the successive batches of 

 eggs deposited in punctures or in the decayed areas of the rind forming 

 about the punctures find conditions increasingly favorable to their ulti- 

 mate success in reaching the pulp. The longer the fruit is allowed to 

 remain on the tree after it becomes ripe, the easier it is for the maggots to 

 reach the pulp. The rind can not withstand indefinitely the persistent 

 attack of successive lots of larvae and the work of decay fungi to which the 

 punctures give entry (PI. XLII, fig. i). Thus, 39 sweet oranges showing 

 an average of 32 punctures to the fruit, gathered from the trees in Sep- 

 tember, 1913, at a time when they were just becoming ripe, developed no 

 larvae. On the other hand, out of 784 sweet oranges gathered during 

 March, 1914, in a very much overripe condition, 254 produced 2,272 

 lan,-£e, or an average of about 9 larvae to the fruit. On account of the 

 looseness of the rind and rag of sour oranges and the greater ease with 

 which the rind is destroyed by decay fungi, these fruits are more quickly 

 infested by the fruit-fly larvae. 



While both sweet and sour oranges in an overripe condition ultimately 

 succumb to the repeated attacks of the Mediterranean fruit fly if per- 

 mitted to remain on the tree, lemons, both of the commercial smooth- 

 skinned and the rough-skinned varieties, withstand these attacks with 

 a constancy that is astonishing. Lemons are not grown in sufficiently 

 large numbers in Hawaii to permit the writers to record observations on 

 large quantities of fruit, but even in orchards where the fruit is heavily 

 punctured infested fruits are very seldom found. In about two years' 

 time only three infested lemons of the commercial variety and one of the 

 rough-skinned variety have been seen by the writers or by fruit-fly 

 inspectors. Out of 235 well-grown and for the most part ripe lemons of 

 the commercial type, picked from the tree, only i developed lar\'ae (this 

 contained 3), and this fruit when picked was partially decayed as a 

 result of a thorn prick. Out of 161 lemons of the same variety, taken 

 from the ground in a very much overripe condition, but 2 developed 

 larvs — I and 5, respectively. No larvae developed in 434 ripe rough- 

 skinned but badly punctured lemons picked from the tree. One partially 

 decayed rough-skinned lemon taken from the ground produced 1 2 larvae. 



The thicker skinned grapefruit, such as the writers have had an oppor- 

 tunity to study best, have shown a strong resistance to the repeated attack 

 of larvae or fungi. Yet these fruits were all grown on less than a dozen 

 trees and in one garden. Twenty-five fruits taken from beneath these 

 trees in a very ripe condition and showing an infestation of the rind 

 equaling that recorded in Table I of the 39 fruits picked from the same 

 trees, produced no larvai in the pulp. However, lar\-ae have been found 

 in a few thin-skinned grapefruit that were in a very much overripe con- 

 dition. 



