190 Maine Agricultural Experiment Station. 1917. 



Process of Oviposition. 



After the process of oviposition was observed with the 

 naked eye in the field, we decided to see with a binocular micro- 

 scope, the formation of the egg chambers or receptacle in which 

 the egg is deposited. Accordingly, about 100 fruit flies captured 

 in the field, were confined in a large breeding jar which con- 

 tained currant branches bearing green fruit. After the female 

 fly alights on a berry, it usually walks about as if seeking a 

 suitable place in which to oviposit. Finally the insect comes to 

 rest, cleans off the egg-laying apparatus with its hind legs, and 

 then the last three segments of the abdomen are bent beneath 

 the body at an angle of about 30 degrees (Fig. 17, F). The berry 

 with the trypetid in this position was now cut off with a pair of 

 scissors, and held below the objective of a binocular microscope. 

 One could readily see the telescoped ovipositor move up and 

 down within the seventh tube-like segment. The distal end of 

 the tube-like segment is applied to the fruit, while the teeth-like 

 projections (Fig. 13, G.) at the end of the ovipositor begin to 

 rasp the epidermis of the berry. The puncturing apparatus 

 often slips on the peel of the currant but apparently the tactile 

 bristles (Fig. 13, G.) near the end of the egg-laying organ assist 

 the pest in locating the scraped area. The claws of the middle 

 and hind legs also slip on the berry and as the legs approach 

 the median line of the body, the fly grasps a new hold. During 

 this rasping period, the mouth-parts are constantly protruded 

 and retracted. Finally the teeth-like projections have scraped 

 a small elliptical hole through the epidermis. The adult now 

 endeavors to force the end of the ovipositor beneath the thin 

 skin of the currant, and as the peel is pried loose in the small 

 hole, the abdomen moves up and down. Next the entire length 

 of the ovipositor is forced beneath the epidermis. A small drop 

 of liquid exudes from the hole. In loosening the cuticle the 

 piercing instrument is thrust in different directions, while the 

 abdomen moves from side to side. The membrane between the 

 egg-laying organ and the tube-like segment becomes swollen at 

 the end of each thrust of the ovipositor. 



After the egg chamber is completed the imago raises its 

 body on its legs, the abdominal segments become distended, and 

 sometimes the proboscis is protuded stiffly. As the muscles of 



