Key for the identification of the species of Micropygomyia (Coquilletimyia) with female characters

1 Spermathecal individual ducts very long, more than 4 times the length of spermathecae (including the basal annulated portion if it is present); spermatheca spherical or wider than long; cibarium with 4–6 posterior teeth diadem-like disposed........ 2

- Spermathecal individual ducts short, not more than 4 times the length of spermathecae (including the basal annulated portion if it is present); spermatheca pear-shaped; cibarium with more than 6 posterior teeth in palisade (except Mi. stewarti that has 4 diadem-like disposed).................................................................................. 6

2 Cibarium with two accessory small teeth intercalated between the medium and external posterior teeth, so there are a total of 6 posterior teeth disposed as diadem; spermatheca wider than long; flagellomere I about 1.2–1.3 the length of labrum, and about 1.7 the length of clypeus; ascoids of flagellomere II reaching or surpassing the apical margin of the article................................................................................... Micropygomyia (Coquillettimyia) vexator

- Cibarium with only 4 posterior teeth disposed diadem-like; other characteristics variable............................ 3

3 Spermatheca spherical, without transverse striations or excrescences at base; individual spermathecal ducts short, not more than three times the length of the genital fork stem........................ Micropygomyia (Coquillettimyia) vindicator

- Spermatheca button-like or spherical but with transverse striations or excrescences at base; individual spermathecal ducts long, longer than four times the length of the genital fork stem...................................................... 4

4 Individual spermathecal ducts thick, its width at middle greater than the width of spermatheca; ascoids of flagellomere II not reaching the apex of the article........................................ Micropygomyia (Coquillettimyia) oppidana

- Individual spermathecal ducts slender, its width at middle smaller than the width of spermatheca; ascoids of flagellomere II reaching or surpassing the apical margin of the article......................................................... 5

5 Ascoids of flagellomere II surpassing the apical margin of the article; flagellomere I about 1.3 the length of labrum............................................................................ Micropygomyia (Coquillettimyia) apache

- Ascoids of flagellomere II not reaching the apical margin of the article; flagellomere I about 1.6 the length of labrum..................................................................... Micropygomyia (Coquillettimyia) nahua sp. nov.

6 Cibarium with 4 posterior teeth diadem-like disposed........................ Micropygomyia (Coquillettimyia) stewarti

- Cibarium with more than 6 posterior teeth in palisade........................................................ 7

7 Common and individual spermathecal ducts striated, the common duct long, about one-half the length of the individual spermathecal duct................................................... Micropygomyia (Coquillettimyia) chiapanensis

- Common and individual spermathecal ducts smooth, the common duct short, about 0.2 the length of the individual spermathecal duct......................................................... Micropygomyia (Coquillettimyia) californica