54 



BULLETIN 276, U. S. DEPAKTMENT OF AGRICULTURE. 



A small pinkish or orange larva (fig. 17) belonging to the family 

 Cecidomyiidae (ApTvidoletes sp.) 1 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 chrysopids, 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 

 Diplosis sp. was an Aphidoletes. 



Other insects which are known to be predaceous on Macrosiplvwm 

 pisi are several true bugs (Podisus maculiventris Say, EuscMstus 

 variolarius P. B., and Triplileps insidiosus Say), a tree cricket, Oecan- 

 thus confiuens H. & II., and a beetle, Podabrus rugulosus Lee. Another 



beetle (P. pruniosus 

 j Lee), closely re- 



lated to the last 

 named, has recent- 

 ly been reported by 

 Mr. H. F. Wilson 

 (1913) as feeding on 

 "the vetch aphis 

 ( Maerosiplium pisi 

 Kalt.?)." A mite 

 {RliyncTioloyli us 

 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 Aphidius Jletcheri Ashm. MS., A. washingtonensis AsTvm., 

 Trioxys (Praon) cerasapliis Fitch, and Megorismus fietcheri Cwfd. 

 In the spring of 1915 Mr. W. B. Hall of this bureau reared ApMdius 

 rosae Hal. and Praon simulans Prov. of this species collected at 

 Wakeiuau, Ohio. 



METHODS OF ARTIFICIAL CONTROL. 



In the clover field the pea aphis is ordinarily held in check by its 

 natural enemies. If ii is apparent- that this aphis is becoming un- 



1 Since the above was written i>r. E. P. Fe! determined Aphidoletes reared at La Fayette, Ind., 



in 1915 from larva- attacking A phis gossypii as .1 . meridionalis Felt. Thoro is little question but that the 

 species an acking M . nisi Is identical. 



Fig. 17. — Larva of the syrphid fly Allograpla ooliqua, which preys upon 

 Macrcisiphuvi -pisi: Enlarged. (Original.) 



