W. M. DAVIDSON 45 



on the sides, a narrow black dorso-median stripe on the caudal 

 half and many small black maculations all over. The anterior 

 face of the puparium is bulbous, the dorsum evenly arched, the 

 venter gently and shallowly concave. The l)ody tapers latei-ally 

 on thf caudal half. 

 Melanostoma obscurum, variety rostratum Hip!;ot (PI. I. fiK- E.) 



Collections of adult females in the field, their transference to 

 insectary cages containing plants infested with aphids, and ol)- 

 servations on the habits of the forms were made as follows: 

 On April 10. 1920, a female fly was placed in a cage containing 

 a cabbage plant infested with the aphid Aphis brassicae Linnaeus. 

 The following day eighteen ova were deposited on leaves and stem 

 of the plant. Seventeen eggs were infertile, the single fertile 

 egg hatching on April 19. On April 10 a second female was 

 placed in a cage enclosing a horse bean plant infested with Aphis 

 nirnicis Linnaeus. The following day eighteen ova were deposit- 

 ed on the bean leaves. On April 17 fifteen eggs hatched. Both 

 the flies died within two days of their capture. Between April 

 10 and 13 one male and six female flies were placed in a cage 

 containing a pea plant lightly infested with the aphid Macro- 

 siphum pisi Kalt. Thirty-three ova were oljtained, and twenty- 

 eight larvae hatched after an incubation period of four and five 

 days. The last fly died eight days after its capture. 



The egg measures .85 mm. in length by .36 mm. in width; 

 elliptic oval, chalk white. The elevations of the chorion are 

 irregular in shape and size, from six to two times as long as broad, 

 the long axis parallel to that of the egg; they are connected by the 

 usual fine I'ldges and occupy in the aggregate considerably more 

 of the surface of the egg than the intervening sunken hyaline 

 spaces do. The eggs were laid singly and not ranked. 



The newly-hatched larva is cylindrical, smooth, and yellow 

 in color. 



liecords of three lai'vae I'aised on an a])hi(l diet in vials in I he 

 insectary at Alhambra, during the months of A])ril and May 1920, 

 indicated a larval stage of nineteen, Iweniy, twenty-tLree days. 

 A fourth larva was full grown in thirty-one days after hatching 

 from tlu> egg l)ut failed to pupate. Food i-ecords of these four 

 larvae were made daily after the first molt, which in each case 



TRANS. AM. ENT. SOC, XLVIU. 



