THE PEAR LEAF-WORM. 



9 



positor at right angles to the sheath (fig. 4, a) . The rhythmical sawing 

 goes on for about 50 seconds more, the two surfaces of the leaf being 

 forced apart to form a more or less oval cavity. The sawing ceases,. 

 and the portion of the ovipositor still outside the leaf is seen to be- 

 come more opaque and greenish. This is due to the passage of the 

 egg and the mucilaginous matter around it. The abdomen moves 

 up and down slightly as the egg is forced into the cavity, and the 

 saws are removed gradually. The actual depositing of the egg occu- 

 pies about 30 seconds, and as soon as the ovipositor is free the anten- 

 nae, which have been practically quiet during the whole operation, 

 immediately resume their rapid vibrations, and the fly moves to a 



Fig. 4. — Ovipositor of adult female of the pear sawflj': a, Last three abdominal segments with 

 ovijwsitor protruding; b, ventral ^'iew of last segments of abdomen witli ovipositor retracted 

 within its sheath; c, ventral view of ovipositor and portion of sheath, showing lateral ridges 

 on inferior blades; d, single superior saw blade; e, single inferior saw Ijlade; o, ovipositor; 

 s, 8Uj)erior saw blade; i, inferior saw blade; sh, sheath; cere, cerci. All highly magnifled. 

 (Original.) 



new place. One female was observed to deposit 5 eggs in 20 minutes, 

 but not all in the same leaf. 



BIOLOGY. 



There is one generation annually. In California, from observations 

 made in 1912 and lOi:^, it was found that adults issued during March 

 and the first half of April, but before the middle of March very few 

 emerged. In Washington, in the spring of 1915, practically all the 

 adults emerged between the 1st and 15th of April. In both localities 

 the period of emergence pro})ably varies more or less with the season. 



Immediately after issuing, the sexes presumably mate and the 

 ff'mulcs oviposit on young pear leaves. 

 57170°— Bull. 4.".8— 16 2 



