THE ORANGE THRIPS. 9 
before eggs were deposited by the newly formed adults, made a 
total of 18.68 days for May to August, inclusive, 1909. For the 
months April to August, inclusive, 1910, this period was 23 days. 
The length of the life cycle of 8 individuals actually recorded from 
the egg, upon potted plants, allowing 3 days, as before, for the 
adults to oviposit, varied from 20 to 36 days. The data upon the 8 
individuals was obtained during September and October, and the life 
cycle was undoubtedly longer at this time than in midsummer. The 
length of life of the adults observed on confined individuals was 
from 4 to 36 days. 
Number of broods. — Although the number of generations in a sea- 
son has not been definitely observed, there are probably four and a 
partial fifth during the period of May to July, inclusive, and one 
generation in each of the months March, April, August, September, 
and October, making in all a possibility of eight to ten generations 
for the season. 
HABITS. 
The orange thrips is very active, especially in the adult form. Its 
abilit}^ to run, leap, and fly is much greater than that of any other 
thrips so far observed by the writers. This activitj^ and their 
small size allow them easily to pass unobserved. The writers have 
frequently seen adults fly from one tree to another 20 feet or more 
distant. They undoubtedly move about to a certain extent, and will 
go from one orchard to another in search of suitable food. Fre- 
quently they will desert the orange groves, between periodical 
growths, for grapes and certain deciduous fruits. 
The orange thrips appear to thrive best in sunny and even very 
hot weather. On cool cloudy clays they are less active and generally 
group themselves on the underside of the leaves. 
Their reproductive habits are only partially understood. Males 
are present part of the year, but usually in more limited numbers 
than the females. 
EXPERIMENTS WITH METHODS OF CONTROL. 
CULTIVATION. 
Attempts have been made to control the orange thrips, in part, by 
means of cultivation, but none of these endeavors has been in the 
least successful. One orchard was hand-raked under the trees and 
the soil stirred up in the fall, with the hope that pupa? would be de- 
stroyed, but results were negative. Another orchard which was 
plowed deeply in the fall yielded similar results. 
