cSO 
spreads out under the aphid and raises it above the surface of the leaf. 
'PI. III., Fig. 4.) fhis cocoon was made by a maggotHke larva that 
had been feeding inside the body of the aphid. The winged braconid 
emerges by cutting nearly a circle thru the skin of the host, usually 
thru the abdomen, and leaves a circular opening with usually a cor- 
responding lid. The mother Aphidins inserts a single egg into the 
body of an aphid. 
Two species of Aphidius are named in the literature as destroying 
M. pisi: A. fletcheri Ashm. MS., reported by Fletcher as having done 
good service in Ottawa, Can., and bred from M. pisi in Delaware by 
Sanderson; and A. ivashingtonensis Ashm., also bred by Sanderson 
under the same circumstances. In Delaware, at least 5 percent of the 
lice were killed by these parasites. 
In Urbana, Aphidius is abundant every season on the clover-louse. 
We have had the adults emerge June 21, 26; July 1, 3, 4, 6, 8, 12, 17; 
August 18, 24; and October 18, 19, — mostly early in July, however. 
An Aphidius larva that I found July 11 spun its oval silken carpet 
under the aphid on the same day ; July 12 the aphid had been raised 
above the leaf and the cocoon was complete; July 18 the adult was 
found, it having issued during the preceding twenty-four hours. An- 
other black larva spun June 18 and the imago emerged June 26. From 
a cocoon made October 12 the adult issued October 19. 
October 10 a female Aphidius was put into a cage containing M. 
pisi, the individuals of which had been reared under glass in a way to 
insure their freedom from parasites. No oviposition was witnessed 
(the mother dying October 21), but November 16 three of the aphids 
showed the cocoons of Aphidius, the aphids having turned brown on 
the day before. These aphids were kept over winter in glass vials, 
and June 10 a winged Aphidius was found to have emerged. It was 
dead then, but certainly did not issue before March 17, when the vials 
were thoroly examined. 
Another braconid, Trioxys (Praon) cerasaphis, was bred in large 
numbers by Fletcher from material collected at Ottawa, Canada, the 
material referred to being by implication M. pisi. 
From what has been given it can be seen that a good many differ- 
ent insects have to do with Macrosiphum pisi in one way or another, 
and that the interrelations of some of them are involved. Thus, 
Meqilla maciilata, which eats M. pisi, is parasitized by Perilitus ameri- 
canus, and preyed upon by Euschistus variolarius — the eggs of which 
are food for one of the proctotrypids. Syrphidce destroy M. pisi and are 
themselves food for the same Euschistus ; furthermore, they are para- 
sitized by Bassus Icetotorius, which, in turn, is parasitized by Pachyneu- 
ron syrphi and Isocratiis vulgaris. 
Among the natural enemies of this aphid is to be counted the 
English sparrow, according to a correspondent of Dr. J. B. Smith, who 
wrote, "It was wonderful to watch them, how soon they cleared up a 
pea-vine. After the sparrows commenced to work, they soon cleared 
up every louse." 
II 
