•'8 BULLETIN 1081, U. S. DEPARTMENT OF AGRICULTURE. 
drop at the puncture. (PL II, at right.) It is possible thereby to de- 
termine easily the number and location of the punctures. 
SEASONAL HISTORY AND OCCURRENCE. 
The insects breed throughout the year in Florida and are present 
in all stages at any month of the year. They have, however, some 
seasonal preferences and occur in much larger numbers at some 
seasons than others. The time of greatest flight of the adults seems 
to be during March and April, while in late summer and fall there 
are very few of them in evidence. This is correlated largely with 
the growth of the host plants, which begin fruiting usually in the 
fall and continue through the winter and spring. Many of the 
plants die down or are cut out in the late spring and new ones set. 
The flies therefore appear on the new fruits in the fall and con- 
tinue to breed in increasing numbers throughout the winter and 
spring. The wild papayas in the hammocks fruit at all seasons and 
always serve as hosts whether or not any of the cultivated sorts 
are available. The generations are by no means marked and vary 
in length from 40 days in summer to TO or more in colder weather. 
In a year's time there are about six generations, although they over- 
lap and are in no way distinct. Moisture in the soil is a very im- 
portant regulating factor in the length of all stages, perhaps even 
more so than changes of temperature. 
POWER OF FLIGHT. 
The distance which the adults are able to travel is not very great, 
for they are not strong fliers. One planting of papayas under obser- 
vation was placed 2 miles from where any other plants existed and 
remained free from infestation throughout the season, the adults 
apparently being unable to cover that distance. In most locations, 
however, there are wild papayas all through the surrounding ham- 
mocks, and these serve to harbor and spread them. 
SUSCEPTIBILITY OF VARIETIES. 
While no distinct varieties of the papaya (Oarica papaya) are 
recognized, there are several types of the fruit grown in the State. 
Several have been introduced from foreign countries and crossed on 
existing types. Then there are the original wild plants which have 
been cross-pollinated on the cultivated plants through natural 
agencies. Through all this cross-pollination there result two rather 
distinct types of fruits, one the small, round, or oval type with 
rather thin skin and flesh and the other the large, oblong fruits which 
usually have thick flesh. One especially fine fruit of the latter type 
has been produced at the Plant Introduction Gardens at Miami, Fla., 
