OP PHILADELPHIA. 69 



yellow, spines of the anterior tibia equal ; posterior tibia some- 

 what dilated. 



Length one-quarter of an inch. -^ . 



2. B. HETEROPTERUS. — Black ; wings with a fuscous anterior 

 margin and uervures. 



Inhabits Maryland. 



Body immaculate with dusky hair, feet rather long, posterior 

 tibia at tip, and first and second joints of the tarsi dilated; wings 

 brown, the costal margin fuscous, nervures difiering somewhat in 

 their arrangements, and the inferior branch of the lower furcate 

 nervure curves backwards at the inner margin so as almost to 

 meet the succeeding nervure at the edge of the wing. 



Length more than three-tenths of an inch. % . 



3. B. ALBiPENNis. — Black ; wings white, with a fuscous stigma. 

 Inhabits Pennsylvania. 



Body with cinereous hair ; head above with black hair ; halteres 

 uscous, scapus brown ; nervures brown ; tarsi black-brown, ex- 

 terior spine of the anterior tibia much larger than the interior 

 one. 



Length three-tenths of an inch. 



This is a very common insect. The wings have a white ap- 

 pearance, and are strongly contrasted with the color of the 

 body, and the brown and definite stigma. The posterior tibia of 

 the male are much more dilated towards the tip than those of 

 the female. 



4. B. ARTicuLATUS. — Black, thorax and feet rufous. 

 Inhabits Pennsylvania. [78] 

 Wings brownish, more particularly at the costal margin, and 



with a very distinct stigma ; poisers pale, dusky at tip ; feet pale 

 rufous, joints and anterior tibia reddish-brown, tarsi dusky at tip, 

 spines of the anterior tibia subequal. 



Length 5 rather more than one-quarter of an inch. 



5. B. ORBATUS. — Black, immaculate ; wings fuscous, the cen- 

 tral connecting nervure wantins:. 



Inhabits Pennsylvania. 



Feet and coxae piceous ; humeral tubercle piceous ; wings 

 dusky, the costal margin particularly ; the transverse nervure of 

 1823.] 



