54 
BULLETIN 276^ U. S. DEPAETMEXT OF AGEICULTUEE. 
A small jDinkisli or orange larva (fig, 17) belonging to the family 
Cecidomyiidie (Apliidoletes sp.)^ is an active enemy of this plant louse, 
and although of small size, being only about one-eighth of an inch 
long, it has a remarkable capacity and is very prolific. It is the 
more effective because it does not attempt to consume all of the body 
fluids, as do the syrphids and clirysopids, but seems only to fed upon 
the juices of the captive plant louse until the latter is dead, soon 
after which the dead plant louse is discarded and another one at- 
tacked. Doubtless the predacious larva mentioned by Fletcher as 
Dij^losis sp. was an Apliidoletes. 
Other insects which are known to be predaceous on Macrosiplium 
fisi are several true bugs (Podisus maculiventris Say, Euscliistus 
variolarius P. B., and TripJdeps insidiosus Say), a tree cricket, Oecan- 
thus conjluens H. & H., and a beetle, Podabrus rugulosus Lec. Another 
b eetle (P. pru niosus 
Lec), closely re- 
lated to the last 
named, has recent- 
ly been reported by 
Mr. H. F. Wilson 
(1913) as feeding on 
'^the vetch apliis 
( MacrosipJium pisi 
Kalt. ?).'' A mite 
(jRliyncliolopTius 
parvus Banks) is 
also known to at- 
tack this aphidid. 
The pea aphis is 
attacked by several 
internal parasites. 
Aphides thus at- 
tacked are inactive and finally die, becoming brown in color, and the 
adult parasite makes its exit from the dead aphis by cutting a circular 
hole in the dried skin. The species hitherto reported attacking this 
aphidid are ApJiidius JletcJieri Ashm. MS., A. wasMngtonensis Ashm., 
Trloxys iPraon) cerasapTiis Fitch, and Megonsmus jietclieri Cwfd. 
In the spring of 1915 Mr. W. B. Hall of this bureau reared Aphidius 
rosae Hal. and Praon simulans Prov. of this species collected at 
Wakemau, Ohio. 
METHODS OF ARTIFICIAL CONTROL. 
In the clover field the pea aphis is ordinarily held in check by its 
natural enemies. If it is apparent that this aphis is becoming un- 
1 Since the above was written Dr. E. P. Felt has determined Aphidoletes reared at La Fayette, Ind., 
in 1915 from larva? attacking Aphis gossypiiasA.meridionalis Felt. There is little question but that the 
species attacking M. visi is identical. 
17.— Larva of the syrphid fly AUograpta obliqua, -which preys v:pon 
Macrosiplium pisi: Enlarged. (Original.) 
