32 



BULLETIN 491, U. S. DEPARTMENT OF AGRICULTURE. 



at any distance from the host plants. In the laboratory, however, 

 the adults often gather in small colonies upon the ceiling. 



THE EGG. 



DESCRIPTION. 



The egg (fig. 2) is pure white, about 2 mm. long, elongate elliptical, nearly 

 flat on the ventral surface, more convex on the dorsal. Eggs are often some- 

 what curved. 



DURATION. 



The duration of the egg stage of the melon fly is very short. Dur- 

 ing the warm summer weather of August, 1914, when during the 

 developmental periods the average mean tempera- 

 ture of Honolulu averaged 79.5° F. and the aver- 

 age range in temperature was only 8.3°, 267 eggs 

 hatched in from 26 to 35 hours after deposition. 

 Of these eggs, which were deposited during a 

 period of 1 hour, as shown by the data in Table 

 V, 119, or slightly over 56.6 per cent, hatched 

 within from 26 to 28 hours after deposition. 

 When the average mean temperature for the incu- 

 bation period averaged 75.6° F. and the daily 

 range in temperature about 10.1°, 81 eggs de- 

 posited between 3.15 and 3.30 p. m. on May 19 

 hatched between 10 p. m., May 20, and 2 a. m., 

 May 21, or within from 31 to 38 hours after dep- 

 osition. At a mean temperature of about 75° F. 

 96 eggs hatched within from 33 to 38 hours after 

 deposition. At the still cooler average mean 

 temperature of 73.6° F. 88 eggs hatched between 

 from 10 to 50 hours after deposition. 



While the data included in Table V give infor- 

 mation regarding the duration of the egg stage in 

 Honolulu or littoral Hawaii in general from April 

 to November, other data show that during January 

 to March embryonic development may require at 

 least 3 to 4 days when the mean temperatures drop to about 69° F. 

 At higher altitudes this period may be appreciably prolonged, due to 

 still lower temperatures, although it is unlikely that at any place 

 where the melon fly is found in Hawaii the duration of the egg stage 

 is more than 6 days. Host fruits containing eggs deposited under 

 normal Honolulu conditions between 10 a. m. and 3 p. m., December 1, 

 were placed, 30 minutes after deposition, in a large refrigerator and 

 held at a temperature varying between 56° F. and 62° F. Examina- 



Fig. 2. — The melon 

 fly : a, Eggs de- 

 posited in cavity 

 in young pumpkin 

 flower ; h, single 

 egg, enlarged. 

 (Original.) 



