OF PHILADELPHIA. 49 



dusky ; antennae twice the length of the head and thorax, second 

 joint very small, third joint as long as as the fourth and fifth 

 taken together, the remaining joints a little dusky, dilated at their 

 bases, and somewhat excavated in their middles ; wings immac- 

 ulate ; nervures, stigma and interstice of the first and second ner- 

 vures, dull-yellowish ; feet pale-brownish ; abdomen somewhat 

 darker than the thorax, with three series of black dots, one lateral, 

 and one ventral ; pleura and pectus whitish yellow. [25] 



Length half an inch. 



The antennae by their length, the second and third joints, and 

 the form of those of the flagellum, show an alliance with the genus 

 Nei^lirotoma, but as they have but thirteen joints, the insect must 

 be regarded as a Tvimla. 



4. T. coLLARis. — Thorax blued-black, lineate with yellow ; 

 tergum yellow with blackish bands. 



Inhabits Pennsylvania. 



Head fulvous; antennae, first and second joints, rather paler 

 than the head; palpi fuscous, pale at base; occiput black: tho- 

 rax blued-black, the collar, two lines each side confluent before 

 and behind, scutel and metathorax, bright yellow, the latter with 

 two confluent blued-black spots at tip ; poisers brown, tip of the 

 capitulum yellowish ; wings with a brown stigma, nervures 

 brown, dififering in arrangement from those of the preceding 

 species and from those figured by Meigen : feet brown, basal portion 

 of the thighs pale ; tergum yellow, segments black-brown on their 

 posterior half; venter pale-yellow, segments dusky on their pos- 

 terior half with a silvery reflection. 



Length a little less than half an inch. 



5. T. ANNULATA. — A dark brown stigma ; abdomen pale, an- 

 nulate with black. 



Inhabits Pennsylvania. 



Antennae fuscous, first and second joints whitish ; rostrum, and 

 lower portion of the front whitish ; vertex and occiput dusky ; 

 palpi fuscous ; thorax yellowish-brown, [26] the indented lines 

 paler ; metathorax light livid ; wings with a brown stigmata, 

 nervures brown, arranged like those of Meigen's fig. 9, pi. 6 ; feet 

 dusky-brownish ; abdomen yellowish-white, incisures and their 

 margins black, forming annulations complete. 

 1823.] 8 



