160 MAINE AGRICULTURAL EXPERIMENT STATION. 1917. 



The integument of the larva is glabrous, finely and regularly papillose, 

 very thin and transparent. The colors of the larva which are therefore 

 resident in the viscera, are during development either an ashy or yellowish 

 green, or more often, a yellowish brown. The young larvae collected from 

 poplar were at first a delicate pea-green but soon changed indoors to the 

 pinkish buff; and all the larvae found on willow at whatever age, as well 

 as those reared indoors from the egg were constantly tan-colored. The 

 full grown larva in any case is "tan-colored," a salmon buff or pinkish 

 buff or warm vinaceous, the dorsum being mostly covered with small, 

 globular masses of adipose tissue of this color. Where these globules are 

 wanting the color is black as follows : A faint, interrupted, black, mid- 

 dorsal line ; and an irregular, elongate, blackish spot, obliquely-placed on 

 either side of each of the principle segments ; about six such spots on each 

 side of the body running from near the mid-dorsal line obliquely laterad 

 and caudad to the lateral margin. Sometimes these black blotches are so 

 large as to give the larvae a prominent, V-shaped, banded appearance, 

 the apex of the Vs directed cephalad on the middle line. 



Growth is rapid, the young larvae apparently reaching full 

 size within ten days of hatching. They are quite active and 

 voracious during this time, moving about over the willow twigs 

 tirelessly if the aphids are scarce. 



However the full-sized larvae are exceedingly sluggish and 

 apparently pass thru a pre-pupal period, from a week to several 

 weeks, during which there is little or no feeding or motion. 



The larvae were found on the under side of the leaves of 

 wild cherry, poplar and dogwood, but on willow almost exclu- 

 sively on the young twigs, their location being determined of 

 course by the position of the aphids attacked. They appear to 

 be quite rare during the first half of the season but occurred in 

 abundance during August, 1916 on willow. 



It seems likely that this may be the species referred to by 

 C. W. Johnson in Psyche Vol. XIII, p. 3, Feb., 1906, as follows : 

 "Figure 7 represents a larva found by Mr. Owen Bryant at Cohasset, 

 during the latter part of September, among some "woolly" aphids on the 

 wild lettuce (Lactuca elongata). The larva was very flat, about 7 mm., 

 in length, slightly roughened, and of a dull yellowish color. It evidently 

 belongs to the Syrphidae. I did not succeed in getting it to pupate." 



Puparium (Fig. 8, I, J). Length 6.6 to 7.75 mm., average 7 mm.; in- 

 cluding the posterior respiratory organ, 7 mm. to 8.2 mm., average 7.6 mm. 

 Width 3.5 to 4.1 mm., average 3.87mm. Height 2.3 to 3 mm., average 2.75 

 mm. In outline elongate oval with nearly parallel sides, the margins prom- 

 inently serrated with the somewhat shrunken lateral processes of the larva, 

 slightly widest a little caudad of the middle. Similar to the larva but the 

 anterior end somewhat narrowed and considerably inflated dorsad. 



It is noticed that the anterior end of the larva is but little retracted 

 caudad on the ventral line ; the larval mouth-parts remaining near the an- 

 terior pole of the puparium. 



