42 NOTES ON MELANOSTOMA (dIPTERA; SYRPHIDAE) 



The majority of the eggs laid in captivity were fertile and 

 eighty-eight larvae issued after an average incubation period 

 of seven and one-half days. 



The newly-hatched larva is pale yellowish-white and unarmed. 

 Just previous to the first molt the general appearance is grayish, 

 the integument being very transparent and smooth. The shape 

 of the larva is cylindrical. Following the second molt the color 

 is a yellowish-brown with a darker dorsal line, the internal 

 tissues plainly visible through the integment. Each body seg- 

 ment bears a transverse row of short pale bristles. The full grown 

 larva is 8.5 mm. in length and 2.3 mm. in maximum width; vis- 

 cera plainly visible through the hyaline integument giving a 

 general color of grayish-brown. Shape sub-cylindrical, slightly 

 flattened dorsally, sides shallowly wrinkled and carinate, each 

 segment armed with short pale spines; anterior spiracles light 

 brown; posterior respiratory tubes brown, fused for their entire 

 length, the combined width twice the individual length, each 

 tube sub-cylindrical. 



In the insectary ten larvae were raised on a diet of aphids, 

 the species consumed being Myzus rosarum Walker, Rhopal- 

 osiphum nervatum Gillette, Macrosiphuni rosae Linnaeus, and 

 M. granarium Kirby. 



These larvae transformed after a larval instar averaging 

 thirty-three and one-half days, the expermental period running 

 from March 20 to April 28. Nine of these subsequently issued 

 as adult flies (five males, four females) after a pupal instar 

 averaging sixteen days. 



The mature flies were smaller than nearly all the specimens of 

 stegnum. that the writer has ever collected in the field, and this 

 fact suggests that the larvae of this species are not normally 

 aphidophagous, or that these larvae were not sup])lietl with 

 their normal host aphids. In California as far as \\w writer 

 recollects the species of Melanostoma have always been abundant 

 in spring, but on only one occasion has he taken a larva in 1lu> 

 field. Theref()i-(> it would appear that either the larvae ni'e not 

 ;iphid()])h!igous or thnt normally th(>y f(HMl at night. In the 

 insectiuy at Alhanibi'a the larvae did most but not all of their 

 feeding at night, and were very sluggish in the daytime, being 



