466 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
Conditions due to altitude cannot be thoroughly discussed until 
more data are collected, but it appears likely that this is not an im¬ 
portant factor, from a practical view-point, if other conditions are 
favorable, as the fly has been collected by the writer at various eleva¬ 
tions, ranging from 1,000 feet to nearly 4,000 feet. In other and more 
tropical regions it has been collected at slightly above sea level, so it 
appears safe to venture that this insect is capable of making itself very 
obnoxious at any altitude up to at least 4,000 feet, if conditions of 
temperature, etc., are favorable. 
There remain to be discussed, heat and drouth. These two factors 
often occur together, and when they are severe are certainly a great 
check to the fruit-fly. Either condition alone may greatly curtail the 
insect’s food by causing fruit-trees to bloom but scantily or by causing 
fruit to drop after it has been formed. When both heat and drouth 
are severe (and especially if prolonged) fruit is certain to be very scarce 
and the fly is consequently checked in its multiplication, in which case 
the fruit of the succeeding season will be comparatively free from mag¬ 
gots. Not only do the above conditions cause a scarcity of the flies’ 
food, but many larvae and pupae are killed outright and the adults are 
greatly restricted as to the time during which they can oviposit. With 
a temperature much over 100° F., larvae are often literally cooked in 
the fruit which fall in the sun, before they can escape and enter the 
soil; and even if they do succeed in burying themselves, such excessive 
temperatures as were experienced in Tucuman during the summer of 
1917 1 were enough to bake them everywhere the sun reached. Such 
a temperature is also fatal to emerging flies, and even the mature 
adults refuse to oviposit during the hotter parts of the day, but remain 
motionless on the underside of leaves, or upon the ground in the shade. 
It has been noticed that after a prolonged hot, dry period, A. frater- 
cuius is much less numerous than usual and that unless very favorable 
conditions for its rapid increase occur during the succeeding winter, 
spring or early summer, the fruit of these seasons will be comparatively 
free from attack by the larvae. However, by the end of summer they 
have generally become numerous enough to again be conspicuous and 
to do a large amount of damage during the succeeding year, unless 
something happens to give them another check. 
Parasites 
This check to their multiplication may be either natural or artificial, 
and in addition to causes of the former kind discussed above, may be 
mentioned parasites. However, these are, as yet, very little known. 
1 January 20, 1917. Maximum at the Experiment Station, 114° F. in the shade 
Maximum in the city of Tucumdn, 118.5° F. in the shade. 
