ART. 4, REVISION OF THE FAMILY THEREVIDAE—COLE. 101 
THEREVA BELLA Krober. 
Plate 11, fig. 137. 
1914. Thereva bella Kréper, Beiheft z. Jahrb. Hamb. Wiss. Anstalten, vol. 31, 
p- 64. 
Male.—Length 9.5 mm. Head black; frontal triangle and face 
silvery white pollinose and white pilose, the pile rather sparsé. 
Antennae blackish brown, the tip of the second and base of the 
third joint vellow; third joint slightly longer than the first (fig. 137); 
first Joint with black bristles and white pile. Palpi yellow, with white 
pile; proboscis largely yellow. Occiput white pollinose and pilose, 
the post-ocular bristles black. Pile on the ocellar tubercle black. 
Mesonotum gray pollinose, the anterior and lateral portions paler, 
with faint indications of two light gray vittae; the pile is reclinate, 
golden yellow, and erect, black, and whitish, whitish on the margins. 
Thoracic bristles black. Scutellum gray pollinose, the base darker, 
with yellowish pile and four black marginal bristles. Pleura gray 
pollinose and white pilose, the pile near the wing base yellowish. 
Halteres yellow, the base of the knob brown. 
Abdomen more or less reddish yellow in ground color, thinly gray 
pollinose and silvery white pilose. The venter and genitalia almost 
wholly reddish yellow, the pile on the genitalia more yellowish. On 
the dorsum of the abdomen a dark-brown or blackish spot at the 
base of the second to the fifth segments and near the middle. 
Structure of the genitalia near that of candidata, the upper portion 
projecting some distance beyond the hypandrium. Coxae and tro- 
chanters black, the former gray pollinose; legs almost wholly yellow, 
the tips of tibiae, apices of first three tarsal joints, and all of the 
last two tarsal joints blackish; empodia yellowish. Pile of femora 
sparse and white; legs with black bristles, the small setulae of tibiae 
and tarsi yellow. Wings hyaline, with a yellowish tinge, the veins 
and stigma yellow; cell M-3 open in the margin. 
Female.—Length 8 to 10.5 mm. Very closely resembling the 
male, but the body more golden yellow pollinose than gray. Upper 
two-thirds of frons golden brown pollinose and short black pilose; 
lower frons and face silvery gray pollinose and golden yellow pilose. 
Pile of first antennal joint largely black. 
Mesonotum slate-gray pollinose, with a rather dense covering of 
short tomentumlike golden pile, the short erect pile black. Base of 
scutellum slate gray, the margin paler, the pile golden yellow. 
Pleura gray pollinose, the pile mixed yellow and whitish. 
Abdomen blackish in ground color, bright golden yellow pilose, 
the base of second and third segments broadly dull black, narrower 
on the fourth; the fourth and fifth with a median basal black spot; 
eighth segment shining blackish brown, the terminal circlet of spines 
