60 



DECIDUOUS FKUIT INSECTS AM INSECTICIDES, 



collected during midsummer, but it is not probable tliat 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 aU seem to await the proper time in February 

 before they come out. If they are prematurely broken out from 



their ceUs during December or January 

 they are active and can fly. but they 

 never seem to leave the ground at this 



time of then 

 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 larvae are just entering the ground: in May, 

 June, and July, after they are all in: in the fall 

 and early winter, to destroy pupae: 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 larvae 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 S 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 larvae come into 

 these and may then penetrate many niches. 



Cultivation during April and May. when the thrips larvae are 

 entering the ground, will kill a few. but it also disturbs and agitates 



: A 



Fig. 17. — The pear thrips: 

 Adult. Much enlarged. 

 (Author's illustration^ 



