PROCEEDINGS OF THE 



ENTOMOLOGICAL SOCIETY OF WASHINGTON 



VOL. 21 JUNE, 1919 No. 6 



A NEW SPECIES OF THE SERPHIDOID GENUS DENDROCERUS 



(HYMENOPTERA). 



BY A. B. GAHAN, U. S. Bureau of Entomology. 



The two interesting new forms here described both run di- 

 rectly to the genus Dendrocerus in J. J. Kieffer's key (Andre's 

 Spec. Hym. d'Eur. et d'Algerie, vol. 10, 1911, p. 10). Both differ 

 from the male genotype in having the antennae serrate instead of 

 ramose and would therefore appear to agree with Atritomus 

 Foerster, which KiefTer, probably correctly, considers a synonym 

 of Dendrocerus. According to Kieffer the male antennae are 

 variable in the genus. 



Dendrocerus, as represented by the species described below, is 

 characterized by having the head viewed from above transverse; 

 antennae inserted at the clypeus,'n-jointed in both sexes, elon- 

 gate and filiform in the female, joints i to 6 of the male flagellum 

 more or less strongly serrate; pronotum entirely concealed from 

 above, mesoscutum with a more or less distinct median longi- 

 tudinal groove, the parapsidal grooves absent or only very faintly 

 indicated at the lateral anterior angles; scutellum longer than 

 broad, convex, very slightly compressed at apex but without 

 an apical process; axillae meeting at inner angles and separated 

 from the mesoscutum by a distinct fine groove; propodeum 

 short, declivous from base or near base; abdomen fusiform, 

 convex above, and about as long as the head and thorax. 



The host record for the species is apparently new for the genus 

 Dendrocerus, other species of which are recorded as having been 

 reared from Cecidomyid and Cynipid galls, and one species from 

 a Coccid on maple. 



Despite the differences pointed out and the widely separated 

 type localities the writer is of the opinion that the two forms de- 

 scribed below r are nothing more than varietal forms of the same 

 species. The greater distinctness of the mesonotal groove and 

 the line on vertex in the paler form are believed to be accounted 

 for by the lighter color which causes them to stand out more con- 

 spicuously. The color of the paler form shows a distinct ten- 

 dency to shade into black and it is possible that a larger series 

 would demonstrate that the differences are merely variations. 



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