ja.i. .5. 19,5 Citrous Fruits and Mediterranean Fruit Fly 319 



by a round white sunken area in the rind which varies in size with the 

 passing of time up to an inch in diameter. Of 560 eggs found in the 

 examination of the abovcymentioned 85 Chinese oranges 471, or 84.1 

 per cent, were unhatched and dead. This same kind of mortality occurs 

 to a less extent in ordinary Hawaiian limes, but with no regularity, as 

 the rind of these fruits in most instances is so thick that the female can 

 not place her eggs within the pulp. 



MORTALITY AMONG LARV^ 



It has been shown that mortality among the eggs occurs in the rind and 

 in the pulp. Lar\'al mortality occurs chiefly during the first instar, either 

 in the egg cavity or in the rag beneath. Though mortality does occur in 

 the pulp to a slight degree, no further notice of it will be taken, as it has 

 little bearing upon the general purpose of this paper. The data in 

 Table I show that of 6,571 larvae recorded as dead but 18 died in the pulp, 

 while 3,166 died in the egg cavities where they hatched, and 3,387 in the 

 rag of the rind. The causes for this mortality of lar\'ae in the rind are 

 threefold : The oil from the ruptured cells, the texture of the walls of the 

 pimcture, and the texture of the rag. 



In the treatment of the eggs with oil, as recorded in Table V, it was 

 found that of the lar\'se hatching from the 163 eggs out of the lot of 1,600 

 eggs sprayed all died either before they were entirely out of the eggshell 

 or before they had crawled much more than one-fourth of an inch. They 

 exhibited a general weakness entirely lacking in normal larvae. Larvae 

 hatching from check eggs were normal and crawled actively to all parts 

 of the containing vials. As the oil sprayed on the eggs and foliage on 

 which the eggs rested appeared to have entirely evaporated by the 

 time of hatching, the writers believe that the few larvae that succeeded 

 in emerging from the eggs died from weakness imparted to the developing 

 embryo by the oil with which the eggs were sprayed rather than from 

 the effect of any oil still on the foliage with which they came in contact on 

 hatching. Subsequent experiments have shown this supposition to have 

 been correct. The writers believe, therefore, that the very large per- 

 centage of the deaths among newly hatched larva: occurring in the egg 

 cavity is the result of the action of the oil liberated during the formation 

 of the cavity — oil which is sufficiently abundant to weaken the developing 

 embryo but not abundant enough to kill the egg. 



To such weakened larva; and probably to many other normal larvae 

 hatching in egg cavities made without the rupture of oil cells the texture 

 of the walls of the cavity present another difficulty. In many host fruits, 

 such as the peach and loquat, the eggs are crowded into and completely 

 fill the cavity made by the female, but shortly after oviposition, possibly 

 as the result of the action of a fluid introduced by the female with the 

 eggs, the flesh of the host slirinks considerably from the eggs, thus usually 



