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a very great loss to the fruit industry. The wide range of food-plants, 

 including pear, apple, almond, cherry, dogwood, acacia, etc., makes 

 its extermination practically impossible. Injury to plants is caused 

 directly by the feeding of the adults and larvae upon the fruit, buds, 

 flowers and leaves, and by the deposition of eggs in the leaves, fruit- 

 stems and fruit. The chief injury to pears is caused by the feeding 

 of the adults in the bud-clusters before blooming. A considerable 

 quantity of sap is exuded ; blue moulds may develop in this and so 

 hasten the destruction of the fruit buds. To secure the best results, 

 it is desirable to apply efficient treatment against the adult in order to 

 reduce the early injury to a minimum, and later to carry out additional 

 treatment against the larvae. Injury to prunes ranks second to that 

 of pears, the adult thrips attacking the flower buds in this case also. 

 The larvae may also cause serious damage to the leaves. Cherries 

 are chiefly injured by the deposition of eggs in the fruit stem and by 

 the feeding of the larvae upon the fohage. The manner of bud growth 

 and blossoming of cherries permits the effective penetration of spray 

 solution more advantageously than is the case with either pears or 

 prunes. In the case of peaches, the thrips feed inside the calyx cups 

 and prevent proper polhnation. The adult emerges from the ground 

 in late winter and early spring, i.e., during February and March, the 

 exact time being dependant on the temperature, rainfall and the 

 presence or absence of grass in the soil. Individuals which emerge 

 early, feed for 15 to 20 days before oviposition, until suitable tissue is 

 available. Egg-laying lasts for about three weeks. The emergence 

 period is associated with the blossoming periods of the different 

 varieties of fruit. Evidence of the migratory habits of the pear thrips 

 has been noticed. Observations indicate that migration in swarms 

 takes place only on sunny days. The habit is probably influenced 

 by a desire for new food supply, better places for oviposition and 

 suitable weather conditions. Migration from badly infested orchards 

 is influenced by the early destruction of the fruit buds. Many instances 

 are known in which thrips have been very numerous one year, less 

 abundant the next, and again very injurious the third. This re- 

 appearance shows that orchards should not be left untreated. Some 

 adults crawl up the tree after emergence from the soil, but the majority 

 fly to the branches to feed and deposit eggs. The only known type 

 of reproduction is by parthenogenesis. Eggs are placed in exposed 

 blossoms, fruit stems, leaves, and in young fruit. The first eggs were 

 observed in San Jos6 on the 9th March, the last in the middle of April. 

 The length of the egg-stage varies from 6 to 30 days, according to the 

 temperature. A single female lays, on an average, 131 eggs, these 

 being placed beneath the epidermis. The larvae appear first on 

 almonds, apricots and plums about the 1st March. The larval stage 

 lasts from 2 to 3 weeks. After being on the tree from 10 to 14 days, the 

 larvae enter the soil to pupate ; the depth varies from 1 to 26 inches, 

 according to the kind of soil. A prepupal stage lasting from 2 to 8 

 months precedes the formation of the pupa ; the largest number of 

 pupae are found in September and October, but pupation begins 

 earher in heavy sedimentary soils than in fight gravel. The duration 

 of the pupal stage varies from 1 to 4 months. The first adults appear 

 in the ground in late October, the number increasing until early 

 January ; the time passed in the soil by the adults is, on an average, 



