240 [April 



Dark yellow, head black, thorax with black stripes, antennae moniliform, 

 their joints short, almost heart-shaped. 



Long. corp. 0.4 — 0.42. 



Head black, shining; palpi brownish; antennae dark brown, reaching a little 

 beyond the basis of the abdomen in the male and somewhat shorter in the 

 the female; two basal joints and the basis of the third brownish-yellow: first 

 joint cylindrical, of moderate length : the second short; joints of the flagellum, 

 especially the middle ones, are not much longer than broad, expanded on the 

 under side so as to appear almost heart-shaped, and connected by short pedi- 

 cels, so as to make the antenna appear moniliform; the last joint is abruptly 

 narrower than the preceding and about twice its length, subcylindrical ; it shows 

 a. coarctation in the middle, which is more apparent in some (fresh) specimens 

 than in others, and then the antennae may be taken for 17-jointed : in the 

 female, the joints of the flagellum arc much less expanded, and only seven or 

 eight intermediate joints have a strikingly heart-shaped appearance; towards 

 the tip, they become gradually narrower; in both sexes, the antennae are 

 clothed with a soft, dense pubescence, much denser on the under side, and 

 much more striking in the male than in the female; besides, each joint has 

 about the middle several verticils. Thorax honey-yellow, with three Idack, 

 shining, often confluent stripes: pectus between the first and second pairs of 

 coxae, black, shining: this Idack coloring is extended upwards, across the pleu- 

 rae, in the shape of a black, but not shining stripe: a black, opaque spot near 

 the base of the halteres, aciculate on its surface: metanotum, or at least its 

 posterior part, Idack, its surface rugose: (very dark specimens, with confluent 

 tlmracic stripes, have all these spots and -tripes darker and more extended: 

 those specimens, on the contrary, which have the thoracic stripes separated by 

 yellow, especially towards the scutellum, have also the other black marks 

 smaller in extent and paler in coloring, often pale brown, and the pectus is 

 black on the sides only, yellow in the middle). A well marked groove extends 

 from the. scutellum along the middle of the intermediate stripe, and is inter- 

 rupted long before reaching thecullare; the intervals between the intermediate 

 and the lateral stripes are rugoso-punctate. Halteres pale, knob dusky. Feet 

 brownish-yellow; tip of the femora, of the tibiae, and of the two first tarsal 

 joints, infuscated ; two or three last tarsal joints brown. Abdomen brownish, 

 last segments darker, venter paler ; genitals brownish-yellow. Wings tinged 

 with brownish-cinereous; stigma elliptical, brownish; inner ami outer sections 

 of the second vein of almost equal length, the latter perhaps somewhat longer: 

 submarginal cell longer than the first posterior; discal cell of variable, gene- 

 rally of moderate size, nearly quadrangular ; four posterior cells : position of 

 the great cross-vein variable, sometimes a little before, sometimes a little be- 

 yond the basis of the discal cell; the small cross-vein is usually wanting, that 

 is, the basis of the submarginal cell is more or less contiguous to the basis of 

 the discal cell ; the extent of this contiguity is variable in different specimens : 

 sometimes the small cross-vein is present, but then it is short ; (among fifteen 

 specimens which I have before me, only four have the cross-vein) ; the fifth 

 longitudinal vein is incurved at its tip. 



Hah. — Washington. D. C. ; New York ; White Mountains, N. II. 

 (iio/i.); Illinois (LeBaron); New Jersey (Cresson). Not rare in May 

 and June. 



Observation. — The aculeus of the male forceps is very often project- 



