December,’18] RUST: anastrepha fraterculus 46$ 
ful development of the larvae. The most propitious time for oviposi- 
tion in peaches seems to be two or three weeks before the fruit would 
normally ripen. At this time they are still firm and green, but the 
pulp loses its excessively hard, dry, astringent qualities and becomes 
sweet enough and moist enough to nourish the young larvae. These 
now develop very rapidly and eat out a large part of the flesh and cause 
the rest to rot so that the larvae are nearly always enveloped in a 
decaying mass which seems exactly to answer their requirements. At 
this stage the fruit colors up and may appear normal except for a few 
small holes which the worms make in order to obtain air, but it is soft 
to the touch, and when opened presents a disgusting mass of corrup¬ 
tion, filled with from three or four to thirty or more wriggling, whitish 
maggots. This decay causes a premature ripening of the unattacked 
flesh and the whole fruit falls to the ground at a time when sound fruits 
of equal age have as yet scarcely begun to ripen. If it still contains 
undeveloped maggots, these are generally able to finish their develop¬ 
ment in the fruit upon the ground. 
Under the favorable conditions of abundant food and suitable tem¬ 
perature which obtain at this season, the egg period is passed in two 
days, larvae develop in another seven to ten days; and the pupal period 
is passed in twelve to fifteen days more, so that we may have adults 
from eggs deposited only three weeks before. This, however, is the 
minimum, attained only under the most favorable conditions, and the 
normal time from one generation to another is very close to thirty days 
in summer. 
By the end of the peach season, the flies have reached their maximum 
number and there is scarcely enough fruit for all to place their eggs in 
during years of heavy infestation, so almost any kind of fruit is used 
for oviposition, but only in certain kinds do the maggots succeed in 
developing. After the peaches have all been destroyed, the females 
turn their attention to later fruits, such as chirimoyas and guavas, each 
of which serve as host for one or more generations of the insect. 
Fruits then become somewhat scarce and not much is left except per¬ 
simmons, which to some extent engage the attention of such females 
as are bent on oviposition. Thus pass the summer months of Decem¬ 
ber, January and February and oranges will soon be in a condition to 
attack. Meanwhile the females content themselves with eating, sun¬ 
ning themselves in warm nooks, or keeping in the shade at mid-day, 
and waiting. They can pass long periods without depositing eggs and 
yet be in perfect condition to resume this function as soon as an oppor¬ 
tunity is presented, so their numbers do not diminish to any very great 
extent during a short scarcity of fruit. By the end of February or the 
beginning of March oviposition begins in oranges but the fruit is gen- 
