60 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
collected during midsummer, but it is not probable that these live 
through the year. They do not mature to form a second brood. 
THE ADULT. 
Adult thrips (fig. 17) are common in the ground in December 
and January, but all seem to await the proper time in February 
before they come out. If they are prematurely broken out from 
their cells during December or January 
we ya they are active and can fly, but they 
Sa L , never seem to leave the ground at this 
, f 5 . 
time of their 
own accord. 
The transforma- 
tion from larva 
to pupa and to 
the adult is a 
slow and grad- 
ual one and 
occupies several 
months. 
METHODS OF TREATMENT. 
CULTIVATION. 
Many ideas have been advanced regarding the 
value of plowing and cultivating at different 
times of the year as remedial measures against 
thrips; especially during April and May, when 
the larve are just entering the ground; in May, 
Fic. 17—The pear thrips: June, and July, after they are all in; in the fall 
(Author's illustration) and early winter, to destroy pups; and during 
February and March, when adults are coming 
out. It has now been clearly demonstrated that much benefit can be 
derived in checking the thrips by plowing and otherwise cultivating 
the ground, if this is done at a proper time and with care. 
Thrips lary penetrate until they can find a protected place where 
no light enters. This may be within 2 or 3 inches of the surface, in 
ground along roadways which is not cultivated and which may be 
partly covered with grass. They usually rest in the 3 or 4 inches of » 
ground immediately below the loose top soil in regularly cultivated 
land, and since they are within 8 or 9 inches of the surface, they are 
thus largely within the reach of the plow. If, from previous improper 
cultivation, the ground is full of cracks and cavities from decayed 
weed stems or roots, or is full of wormholes, the larve come into 
these and may then penetrate many inches. 
Cultivation durmg April and May, when the thrips larve are 
entering the ground, will kill a few, but it also disturbs and agitates 
