912 Charles Paul Alexander 



n Second anal vein arcuated, before its tip bent strongly toward the first. [Eriopt^a 

 Zotricha O. S. Proc. Acad. Nat. Sci. Phila., p. 226. 1859. .0 holotncha (a S. 

 Anal veins divergent. [Trans. Amer. Ent. Soc, vol. 42, p. 140, pi. 10, fig 6 1916] 



0. pal-pahs Dietz 



12 Antennae of both sexes shorter than the thorax , . ' , V M ' j,-i • : ■ • • ^^ 



Antennae of the male approximately as long as the whole body, beadlike m struc^ 



13. Second anal vein arcuated, before its tip bent strongly toward the first 14 



Anal veins divergent | 



14. Thorax reddish Jg 



Thorax not reddish • ■ • ; • ■ ■ • • j' „^c, 



15 Mesonotum with a dark median line; male hypopygium with two pleural appendages 

 which are almost straight; gonapophyses elongate, black, profoundly bihd; penis 

 guard not trifid. [Rhijpholophus ruhellus O. S. Mon. Dipt. N. Amer part 4, p 144 



pi 1 fig 15. 1869.] (Plate XXXIV, 60.) 0. rubella (O S.) 



Mesonotum without a dark median line; male hypopygium with the pleural appendage 

 a single curved hook; gonapophyses strongly curved, entire hooks; penis guard tnhd 

 at apex [Can. Ent.: vol. 49, p. 24-25. 1917.] (Plate XXXIV, 59.) 



'^ O. mmbipenms Alex. 



16. Stigma distinct, dark brown, the marking continued down onto the cot± [Erioptera 

 meigeniiO.S. Proc. Acad. Nat. Sci. Phila., p. 226. 1859.] (Plate XXXIV, 61_) 



O. meigenii (U. o.) 

 17 



Stigma indistinct or lacking • ■ • „ V ' ' Vv r^il ' 'ij Uro 



17 Thorax and antennae light yellow. [RMjpholophus parallelus Doane. Eht News 



■ vol 19 p ''02 1908.] 0. parallela (Doane) 



Thorax brown, with a grayish pruinosity and a rather broad darker stripe; antennae 

 brown. [Trans. Amer. Ent. Soc, vol. 42, p. 141. 1916.] perplexa Dietz 



18. Mesonotum with a darker line on either side; ninth sternite produced into a median 



spatulate lobe. [Trans. Amer. Ent. Soc, vol. 42. p. 142-143, pi. 10.^fig^| J^ia]^^^ 



Mesonotum reddish brown with a median brown stripe; ninth sternite produced into 

 two flattened lobes that project far caudad. [Trans. Amer. Ent. Soc, voL 42, p. 14,i- 

 144, pi. 10, fig. 9. 1916.] 0. deviala Dietz 



19. Anal veins convergent 2i 



Anal veins divergent • ; ,'A' " ^\ " ' V'AnL' oV 1Q17 1 



20. Segments of flagellum shorter, without pale apices. [Can. Ent., vol. 49, ^-^-J-^^^J 



/p, . "V"V"VTV 63 "1 Tnttsuctiu /\ica. 



Antennal segments ' elongated," the ' segments attenuated and the apices pale. 



[Rhypholophus monticola O. S. Mon. Dipt. N. Amer., part 4, p. 145 1S69. 



f PI te XXXIV 6"' ) ^- ^"''"^'^com (U. b.) 



21 Reddrsh brown; meionotum' with' an' indistinct brown median stripe^ [Trans. Amer. 



Ent. Soc, vol. 42, p. 144-145, pi. 10, fig. 10. 1916. • ._.0 dtvergens Dietz 



Dark brown; mesonotum with three darker brown stripes. [Can. Ent., vol. 4y, p. -D. 



1Q17 1 fPl te XXXIV 64 ) ^' "^^f/^'cera Alex. 



(0 megaccra is probably the same as d.'diwns, the latter name preoccupied 



by 0. divergens Coq. [1905].) 



The small flies that make up this characteristic genus are very com- 

 mon, appearing in small, swarms under overhanging ledges, along the 

 lower face of an inclined tree, or in similar situations. The early sprmg 

 species are Ormosia innocens, 0. nubila, 0. meigenii, 0. holotricha, and 

 others; 0. apicalis, 0. megacera, and 0. mesocera occur in early summer; 

 0. nigripila, 0. nimbipennis, 0. monticola, and 0. abrwrmis are late 



