158 MAINE AGRICULTURAL EXPERIMENT STATION. 1917. 



is of such a size that about forty of the ladder-like chains are traversed 

 in passing from one pole of the egg to the other, the elevated bodies be- 

 ing approximately 0.02 mm. apart. 



The eggs have been taken in the field only on the small 

 twigs of willow directly among the aphids, Pterocomma smithiae 

 (Monell), in early August. They were also deposited in cap- 

 tivity from a female caught hovering about this infestation in 

 late August. There is at least one other time of occurrence for 

 the egg stage, those giving rise to the first generation of larvae 

 in the spring probably being deposited in June. It is further 

 probable that adults emerging in September, (as specimens in 

 the laboratory did) may deposit eggs for a third generation ; 

 although it seems doubtful if these larvae could mature at this 

 latitude before cold weather cut short their food supply. 



The eggs are glued by the ventral surface to the bark of 

 the young twigs, and occur singly. 



The duration in the egg stage, from eggs deposited indoors, 

 was between 2^5 and 3^4 days, while some eggs brought in from 

 the field on August 8 did not hatch until August 13, this stage 

 exceeding five days. At time of hatching the micropylar end 

 of the egg shell is pushed off as a roughly circular cap, leaving 

 the rest of the shell intact. 



Larva (Fig. 8, C to H). The newly hatched larva (Fig. 8, C) is 

 elongate ovate in outline with the posterior end truncated or even excised. 

 It measured 0.95 mm. in length by 0.39 mm. in its greatest width, a little 

 caudad of mid-length. It thus appears, from the first, proportionately 

 broader and is more flattened than the other described aphidophagous 

 species. The color is pale yellow more or less blackened on the mid-dor- 

 sal line by the interrupted pulsating dorsal blood-vessel. The whitish 

 longitudinal tracheal trunks also are faintly visible thru the integument. 

 The young larva appears very bristly (cf. Syrphus americana Wied. 1 ), 

 the segmental bristles being quite conspicuous. There are eight trans- 

 verse rows of twelve bristles each, besides additional ones on the termi- 

 nal segment, the individual setae measuring about 0.0666 mm. in length, 

 of two segments, the basal one about 0.008 mm. long and of equal diam- 

 eter, the distal one 0.06 mm. long and about 0.0035 mm. in diameter, taper- 

 ing slightly to the tip. The integument is wrinkled transversely and the 

 lateral margins are irregularly serrate. 



The posterior respiratory tubes are well separated, fairly prominent, 

 nodular; the slit-like spiracles short and situated near together. There 

 is no integumental vestiture in addition" to the segmental setae. 



As growth continues the larva becomes more and more flattened so 

 that by the time it is full grown it is more than half as broad as long, 



'The Ohio Naturalist, Vol. VII, No. 5, p. 479, Mch. 1912. 



