16 PROCEEDINGS OF THE NATIONAL MUSEUM vol.74 



middle; nervellus broken below middle, its upper abscissa nearly or 

 quite perpendicular to cubitella; legs slender, front tibia in female 

 not inflated. Abdomen fusiform, narrower in male, coarsely punc- 

 tate, first tergite bent, postpetiole broad, usually with a prominent 

 flange-like carina on lower margin; sheath much shorter than 

 abdomen. 



The North American species may be distinguished by the follow- 

 ing key : 



1. Occipital carina prominently toothed a short distance before reaching liypo- 



stt.mal carina ° (fig. 16) ; abdomen black, the tergites conspicuously banded 



with white apically albomaculatus (Cresson). 



Occipital carina not prominently toothed (fig. Ic) ; abdomen red on black 

 with at most the apical tergites narrowly white apically 2 



2. Apical carina obsolete medially or much weaker than at apophyses ; areola 



wanting ; apical tergites margined with white multicolor, new species. 



Apical carina of pi'opodeum distinct throughout, apophyses not much stronger 

 than middle; areola more or less defined (fig. 3e) ; apical tergites not 

 margined with white 3 



3. Frontal horn black agnatus, new species. 



Frontal horn white paludatus (Cresson). 



LISTROGNATHUS ALBOMACULATUS (Cresson) 



Synonymy and description under varietal heading. 



A very variable species that is divisible on the basis of specimens 

 studied, into five more or less distinct varieties, recognizable by the 

 following key : 



1. Lower division of metapleurum partly white 2 



Lower division of metapleurum entirely black 3 



2. Hind tibia and basitarsus red rufitibialis, new variety. 



Hind tibia black or blackish with a subbasal yellow annulus, basitarsus 



yellow multimaculatus, new variety. 



3. Hind coxae red and white ; fore wing in female with a distinct cloud below 



stigma variety nubilipennis (Cresson). 



Hind coxae black or black and white 4 



4. White bands of abdomen in female, at least on tergites 2 and 3 interrupted at 



sides ; mesoscutum immaculate, mesopleurum nearly or quite so ; face in 

 female medially immaculate ; antenna in male without white annulus. 



variety sagax (Provaucher). 



White abdominal bands entire ; mesoscutum and mesopleurum with white 



spots ; face in female usually more or less white medially ; antenna in male 



with white annulus variety albomaculatus (Cresson). 



LISTROGNATHUS ALBOMACULATUS variety ALBOMACULATUS (Cresson) 



Figs, la-b, 2e, 3d, Ge 



Mesostenus albomaculatus Cresson, Proc. Ent. Soc. Philadelphia, vol. 3, 18&4, 

 p. 313, female.— AsHMEAD, Smith; Ins. of N. J., (1899) 1900, p. 570. 

 Type.— No. 1108, Acad. Nat. Sci. Phila. 



s The carina running backward from the ventral articulation of the mandible along the 

 outer side of maxilla. 



