THE PEAR THRTPS IN CALIFORNIA. 39 



show a single one going through this procedure. The usual method 

 as shown by observations during the season of 1910 is as follows: 

 The female starts the ovipositor into the tissue by working the 

 abdomen up and down, gradually forcing the ovipositor its full length 

 into the tissue. After this is done the thrips remains quiet for a 

 short interval while the egg is passing out between the plates of 

 the ovipositor. When finished, the female vibrates her antennae and 

 jerks out the ovipositor. The prevailing posture during the whole 

 period of oviposition is with the abdomen arched and the legs spread 

 apart wider than when in walking. The average time required for the 

 operation by a number of individuals observed during the season of 

 1910 ranged from three to five minutes. After depositing an egg the 

 female usually resumes feeding for a short interval, but some indi- 

 viduals have been observed to deposit two and three eggs in suc- 

 cession without any feeding between times. The number of eggs 

 that a female can deposit in a day is probably not over seven or eight, 

 as the abdominal cavity is not large enough to hold more at one time. 



EGGS. 



PLACE OP DEPOSITION. 



The eggs are always placed in the tenderest portions of the plant 

 tissue, such as exposed blossoms, fruit stems, leaf stems, ribs of the 

 leaves (preferably the midribs), and the leaf edges. Still others are 

 placed in the young fruits. The pear thrips apparently prefers to 

 oviposit upon cherries if a cherry tree is at hand, as the fruit and leaf 

 stems, on account of their length and tenderness, offer excellent places 

 for oviposition without making it necessary for the thrips to move 

 over a large area. However, the small prunes and the stems, as also 

 the stems and midribs of the young leaves of both prunes and pears, 

 are well suited for oviposition by this species. The counts in Table 

 VIII were taken upon leaf stems and fruit stems of French prunes and 

 show the comparative percentage of eggs deposited in each; they also 

 show the inability of the different spray mixtures to kill the eggs 

 within the plant tissues, as these stems in question had been sprayed 

 two days previously with a combination of tobacco extract and dis- 

 tillate emulsion. 



