8 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



surrounding tissue be flexible and moist, for the egg covering is elastic 

 and the canbryonic thrips within increases in size very noticeably 

 before the larva issues. 



There is space within the adult insect's body for only a few eggs at a 

 time— seven or eight. A thrips probably places only a few eggs dur- 

 ing a single day. She feeds for a time, deposits an egg, and then 

 moves to another place, and later to still other places, and these may 

 be all on one or scattered on several trees. The adult thus spreads 

 her progeny from tree to tree wherever she goes. Nothing seems to 

 hinder thrips which may be set on ovipositing. They have been ob- 

 served placing eggs at all hours of the day and 

 night and under all conditions of weather. 

 The period of oviposition lasts for several 

 weeks, or during practically all of the life of 

 the adult insects. Injury from oviposition 

 is most conspicuous on cherry trees. Oper- 

 ating at the base of a cluster of fruits, a few 

 thrips will cut several incisions and place as 

 many eggs in a single stem. This so weakens 

 the stem that it fails to perform its usual 

 function, and the rapidly developing cherry 

 soon becomes yellow, and falls. Thrips seem 

 to prefer the cherry to other varieties of fruits 

 as a place for ovipositing during the later sea- 

 son, and this fruit suffers severely from 

 ovipositing, though it may escape the first 

 feeding injury. The result is a heavy drop- 

 ping of half-grown cherries, which in badly 

 infested regions means almost the whole crop. 

 Numerous leaf and blossom stems in which 

 eggs had been placed were closely watched 

 to determine the length of the egg stage. In 

 many cases these stems became dry during 

 confinement in the laboratory, and almost in- 

 variably from these no thrips issued. Eggs need moisture for their 

 preservation and development, and young thrips must have tender 

 and pliable tissue through which to emerge. The egg stage lasts, 

 approximately, four days. 



THE LARVA. 



-ji\ 



Fig. 4.— The pear thrips (£u- 

 thrips pyri): larva. Much en- 

 larged (original). 



It is interesting to watch, with the aid of a strong lens, a young 

 thrips issuing from the egg. The tiny incision in the stem of a 

 blossom or leaf shows where an egg has been placed, and the enlarging 

 egg within, causing a swelling in the plant tissue at the summit of 

 which is the incision, indicates that the insect is about ready to 

 emerge. The first sign of life is the appearance, pushing out from the 



