PROC. ENT. SOC. WASH., VOL. 23, NO. 3, MAR., 1921 63 



centages of parasitism ranging from twenty-five to thirty per- 

 cent, indicating that the parasite may prove of great importance 

 in the natural control of the apple maggot. 



REFERENCE. 



1912. QUAINTANCE and JENNE. Bur. Ent. Bull. 103, pp. 140-142. 

 1918. BROOKS, F. E. Bur. Ent. Bull. 730, p. 14. 



REVISION OF THE GENUS LYGAEUS FAB. (HEMIPTERA-HETER- 



OPTERA). 



H. G. BARBER, Roselle Park, N. J. 



Characters of the genus. Pronotum either without a median longitudinal keel 

 or with a keel not reaching anterior margin; posterior margin straight before 

 scutellum. Scutellum depressed, with a longitudinal median keel commonly 

 joined to a median or premedian transverse ridge. Metapleura with posterior 

 margin straightly or somewhat roundly truncate not oblique, the anterior and 

 posterior margins of this nearly parallel. 



Corium almost or quite impunctate; its posterior margin straight. Mem- 

 brane not at all or usually narrowly but never with the apex more widely white 

 margined; rarely entirely or for the most part clear of whitish. Head (except in 

 Melanocoryphus Stal) with a red or pale spot or longitudinal fascia near base; 

 eyes in contact with the anterior margin of pronotum. Species mostly black 

 marked with red or sometimes with the latter color predominating. 



Key to Subgenera and Species. 



1. Pronotum black provided with a postmedian transverse red band or three 



red spots, remote from posterior margin. Venter most commonly red 

 with fascia at anterior angles of segments 2-5 and all of sixth and genital 

 segments black or most rarely (formosns) venter entirely black. 

 Odoriferous orifices black. Head with red fascia at least at base. 

 Larger species, 10-12 mm. 



Subgenus (Graptolomus Stal) Lygaens Fab., Van Duz... 2. 



Pronotum unprovided with a transverse postmedian red fascia, remote 

 from posterior margin. Species smaller . 6. 



2. Clavus pale margined within, never furnished with a subapical black spot. 



Venter of abdomen entirely black. formosus Blanch. 



Clavus never pale margined, either entirely black or anteriorly red; 

 opposite apex of scutellum furnished with an opaque black spot. 

 Venter red marked with black... 



3. Membrane in great part pale with fuscous veins. Broad margins of all 



pleurae posteriorly, propleurae anteriorly, bucculae and acetabulae 

 pale fusco-reddish .. 



Membrane either entirely black or most commonly pale margined with 

 concolorous veins, with or without white discal spots. Bucculae, 

 acetabulae and margins of pleurae not pale 



