EEISTALIS. 243 



The optic nerve is very large, cylindrical, and of a diameter equal 

 to the length of the brain, upon the side of which it is supported ; 

 it terminates in a very large bulb corresponding to the eye. The 

 species may be grouped thus : 



#. Marginal areolet not reaching the external border of the wing. 



6. Mediastinal areolet much longer than the marginal areolet. 



Species 1-3. 



6 b. Mediastinal and marginal areolets nearly equally long. 

 c. Antenna? with the fifth joint bare. Species 4, 5. 

 c c. Antennae with the fifth joint plumose. 



d. Body very hairy. Abdomen almost globose. Species 6. 

 d d. Body merely pubescent. Abdomen conical. Sp. 7-12. 

 a a. Marginal areolet extending to the external border of the wing. 

 Species 13. 



1. tenax, L. s. n. ii. 984. 82 (1767); Rm. ; Shi.; Fb.; Shr. ; 

 Gm. ; Mg. ; Pz. ; LI. ; Fin. ; Mq. ; Lw. ; Ztt. porcina, Dg. arbus- 

 torum, L. ; Shr. apiformis, Gf. vulgaris, Spl. -fuscus, Spl. campes- 

 tris, Mg. ; Mq. hortorum, Mg. Piceus, scutello fulvo, abdominis seg- 

 mentorum marginibus posticis maculisyue duabus lateralibus basi fulvis. 

 Long. 7 ; alar. 14 lin. 



Piceous, clothed with tawny hairs. Head clothed with black hairs 

 on the crown and with whitish hairs in front, bare and shining above 

 the antennae and on the scapula above the peristoma. Antennae black. 

 Scutellum dull tawny. Wings colourless, slightly tawny along the 

 costa. Halteres tawny with piceous knobs. Abdomen with a large 

 transverse triangular more or less distinct tawny spot on each side near 

 the base ; hind borders of the segments tawny. Var. /3. Wings more 

 or less clouded with brown beneath the middle of the fore border. 

 Var. y. Abdomen with a narrow interrupted tawny stripe on the 

 second segment, spots near the base very large and distinct. 



GeneraUy distributed. (E. S. I.) 



2. fumipennis, St. ill. pi. 47. f. 3. Niger, antennis scutelloque 

 ferrugineis, alis nigro-fuscis apice margineque postico cinereis, abdomine 

 basi ferrugineo-bimaculato segmentorum marginibus postico luteis, femori- 

 bus posticis crassis, tibiis posticis latis arcuatis. Long. 6 ; alar. 12 lin. 



Black, mostly clothed with ferruginous hairs. Head testaceous in 

 front, with a ferruginous scapula ; vertex clothed with black hairs. 

 Antenna and scutellum ferruginous. Wings dark brown, dark grey 

 at tlie tips and along the hind border. Abdomen with a large ferruginous 

 spot on each side of the base ; hind borders of the segments luteous. Legs 

 black, clothed with black hairs; hind femora thick', tibiae yellow 

 towards the base ; anterior tibiae brown ; hind tibiae broad, much 

 curved; tarsi ferruginous. 



Very rare. In Mr. Stephens' s collection. (E.) 



