Key to the Efferia of the Eastern United States


 

 

This key was created by blending the Efferia keys from Bromley's Robber Flies of Texas paper with new information from the Wilcox update article Efferia Coquillett in America North of Mexico from the 1960s which has its own keys. Additional species were also added since Wilcox. This key can be used for Oklahoma and Texas and the eastern US. It will work for most New Mexico species. Efferia of the NW and California are not included if they are restricted to those ranges. If you are keying a robber fly from AR, LA, MO and east then the red highlighted species are of concern (only 11 species). Any other species that is found in the east is of interest. The majority of species occur centrally and in the SW and Texas.

 

Bromley's key attempted to use characters which would apply to either sex. The female Efferia are difficult. And some of the species females will likely not be keyable to species. Female characters are listed where known and will be added as I obtain more information. Key insertions were made with decimal numerals to make insertion easier. The decimals do not imply relationships of any kind in the key.

 

Note that the subgroups of Efferia that were defined by Artigas as full genera are used here. Wilcox used these same splits for the species arrangements inside the key but did not consider them as generic level divisions. Note that some authors still use Efferia as the genus for all species in this large group.

 

 

1  Furcation of the third vein distinctly before the base of the second posterior cell making the second submarginal cell long

                                                                           2

1 Furcation of third vein opposite or beyond base of second posterior cell

                                                                                        18

 


 

2  Three submarginal cells (check both wings) (Efferia/anomala group)

                                                                          3

2 Two submarginal cells

                                                                           5


 

 

3   Bristles of palpi, scutellum, and upper occiput black (18-20mm)

                                 3.5

3  Bristles of palpi (usually scutellum), mystax, and upper occiput pale

                                                 4

 


 

3.5  Femora reddish posteriorly, usually larger flies (25-32mm); female ovipositor 4.5-5mm

Efferia anomala (Bellardi)

(KS TX AZ  NM)

3.5  Femora black, smaller flies; male abdominal segments 1-7 white pollinose, 2-5 with white parted hairs like Pogonioefferia; female abdomen white pollinose, dorsum of 7 sub-shining black (13-25mm), ovipositor 4.2mm

Efferia luna Wilcox

(NM  KS TX)

3.5"  Femora black, male abdominal segments 1-5 laterally silver and 6 and 7 silvery; female ovipositor 5.2-6.3mm, abdominal segments 2-5 gray laterally, 7 black-haired

Efferia incognita Forbes

(NM TX)

 


 

4  Male abdomen with white hairs parted at middle and directed outward (15-30mm)

Efferia candida Coquillett

(AZ NM KS OK)

4 Male abdomen wholly black haired with six and seven white pollinose and without hairs parted at middle and directed outward (16-20mm)

Efferia completa (Macquart)

(TX)


 

 

5  Rear of thorax and scutellum with abundance of bristles, male abdominal segments of six and seven silvery, female with tip of oviduct furcate from above (Pogonioefferia/rufibarbis group)

                                                                                 6

5 Male abdomen usually with several segments silvery, female with tip of oviduct never divided from above. Male except in a very few cases, with one or more abdominal segments bearing long white hair parted at middle and directed outward (stramineus group)

                                                                                                 7


 

Scutellar bristles black; mystax yellow, body and wings dark colored (16-30mm)

Pogoniefferia pogonias (Wiedemann)

(EXT)

 

 

6'  Scutellar bristles largely or in part white

6.5

 

 


 

 

6.5   Discal hairs of scutellum black, sometimes a few white laterally; mystax white with 4-5 black bristles; dorsum of abdominal segments 1-4 or 5 black haired and usually venter of 2 and 3; female abdominal segments 1-7 all broadly black haired; ovipositor 4.2mm

Pogoniefferia helenae (Bromley)

(SWestern and KS OK TX)

 

6.5  At least some of the hairs of the base of scutellum white; mystax white with a few black bristles, body gray pollinose, abdominal segments 1-2 with black hairs dorsally, wings hyaline (14-24mm); female abdomen all white haired; ovipositor 4.6mm

Pogoniefferia bicaudata (Hine)

(EXT Western & TX OK KS)

 


 

 

7   Furcation of third vein at or before middle of distance between the base of the second posterior cell and the small cross vein

                                                  8

7  Furcation of third vein distinctly beyond the middle of the distance between the base of the second posterior cell and the small cross vein

                                               14

 


 

8  Male abdomen without long hair parted at middle and directed outward on one or more segments

                                                                                 8.5

8 Male abdomen with long hair parted at middle and directed outward on one or more segments

                           10

 


 

 

8.5  Posterior side of femora red

                                        9

8.5 Posterior side of femora otherwise

                                                             9.2

 


 

9   Male genitalia from side view plainly divided at tip, swept back, oviduct conical, abdomen without interrupted gray pollinose bands, scutellum with black bristles; light brownish pollinose species (22-30mm)

Triorla interrupta (Macquart)

(Extensive)

9   Male abdomen white to grayish pollinose, dorsum of 1-6 brown, scutellum with white bristles (22-28mm)

Pogoniefferia varipes (Williston)

(AZ NM KS CO TX WY OK)

 


 

 

9.2   Very small species, abdomen grayish white pollinose, terminalia yellowish-red, 10-12mm

Pogoniefferia wilcoxi (Bromley)

(TX AZ NM)

9.2  Larger species

     9.5

 


 

 

9.5   Male abdomen black, dorsum 2-5 broadly subshining brownish-black, tibiae basally reddish yellow, head black, terminalia black (22-28mm)

Pogoniefferia texana (Banks)

(TX AZ OK KS NM)

9.5  Yellowish pollinose species, the abdomen silvery pollinose; male genitalia from the side view tapering to a point, head reddish, terminalia reddish (18-25mm)

Pogoniefferia bexarensis (Bromley)

(TX NM OK)

 


 

 

10  Mystax yellow, male with abdominal segments three to seven inclusive white haired

Pogoniefferia rapax (Osten Sacken)

(AZ NM UT TX CO KS)

10 Mystax not yellow

                 10.5

 


 

10.5 Small, fragile species 10-13mm, male abdomen with white parted hairs 2-7

Pogoniefferia mesquite (Bromley)

(TX)

10.5 Larger species, male with fewer than all segments 2-7 having long white parted hair, one species with long parted hair on 2-4 and short parted on hair5-7

                                                                    11

 


 

 

11  Hypopygium plainly notched on apical border

                                                                        12

11 Hypopygium not notched on apical border

                                                                        13

 


 

 

12  Thorax yellowish pollinose, first two segments of male abdomen like thorax, legs black, extreme bases of tibiae reddish yellow (18-23mm)

Pogoniefferia argentifrons (Hine)

(KS TX OK NM SD)

12 Thorax gray pollinose, first two segments of male abdomen like the following ones (23-25mm)

Pogoniefferia argyrosoma (Hine)

(NM CO KS OK AR TX)

 


 

 

13 Hypopygium truncate at apex; yellowish brown; abdomen gray (22-30mm)

Pogoniefferia truncata (Hine)

(AZ CO UT NM)

13 Hypopygium rounded at apex, short; yellowish gray pollinose species (18-23mm)

Pogoniefferia pallidula (Hine)

(EXT Western & KS OK TX)

 


 

 

14   Femora largely red, especially posteriorly; male abdominal segments two to six inclusive with black markings (23-25mm)

Pogoniefferia triton (Osten Sacken)

(AZ NM KS TX) 

14  Femora all black

                                                                                        15

 


 

 

15   Mystax white

                                                           15.5

15  Mystax yellow, scutellum with yellow or black hair and bristles

                                                        16

 


 

 

15.5   Very small species (12mm), mesothorax posteriorly white haired; female ovipositor 2.2-2.7mm

Pogoniefferia pilosus (Hine)

(AZ TX NM)

15.5  Larger species, mesothorax black haired

                                                                                       15.8

 


 

 

15.8   Male abdominal segment 3 posteriorly and 4-7 silvery pollinose, posterior margin of 3 and 4-6 with white parted hairs

Pogoniefferia monki (Bromley)

(Probably not a true species, types lost and no other specimens known.

(TX)

15.8  Male abdominal segment 3 apically and 4-7 with dense white parted hair; female ovipositor 2.8-3.0mm

Pogoniefferia parkeri (Wilcox)

(AZ TX NM)

 


 

 

16   Scutellum with yellow hair and bristles (sometimes brownish in prairiensis, but not black)

16.5

 

16  Scutellum with black hair and bristles (females of P. prairiensis may have mixed coloration or darker hairs on scutellum but ovipositor much shorter than the two species in 17 split)

                                                                  17

 

 


 

 

16.5   Mystax bright yellow, scutellum with long yellow hair and bristles (16-24mm); male abdominal segments 6-7 silvery, no white parted hairs; female scutellar hairs as in male, nearly as long as bristles; ovipositor 3.1-4.1mm

Pogoniefferia auripila (Hine)

(TX OK)

 

 

16.5   Mystax yellowish golden, scutellar bristles brownish yellow, discal hairs about half the length of bristles; male segment 7 silvery (21-26mm); no silvery hairs on female abdomen, ovipositor 3.6

Pogoniefferia prairiensis (Bromley)

(KS OK TX AR)

 

 


 

 

17   Male, first three abdominal segments without silvery markings though third may have minimal posterior silvering, female uniformly yellow pollinose, robust species (23-32mm); female ovipositor 5.6-6.2mm

Pogoniefferia plena (Hine)

(KS OK TX)

 

17  Male, only first two abdominal segments without silvery markings; female, abdomen with a series of large black markings dorsally, one to each segment (24-30mm); female ovipositor 4.6-6.5mm

Pogoniefferia nemoralis (Hine)

(LA KS OK OH VA WV NC GA SC AR)

 


 

 

 

18  Posterior branch of third vein curved backward at tip, meeting the costa at or beyond apex of wing (Nerax/aestuans group)

                                                                                                        18.5

18 Posterior branch of third vein curved forward meeting the costa plainly before the apex of wing

                                                                                                                           23

 


 

 

18.5  Male abdomen with half of segment 2 and 3-7 largely white pollinose with white parted hairs; female abdominal segments 2-5 black dorsally and ovipositor short, less than 4mm in length

Nerax beameri Wilcox

(TX)

18.5 Male abdomen at most with 4-7 largely white pollinose and without white parted hairs; female segments varied with ovipositor longer than 4mm except in aurimystacea

                                             19

 


 

 

19  Tibiae partly reddish or yellowish, hypopygium from side view, most prominent apically on upper half, small species (10mm), mystax black with gray hairs intermixed, costal border not dilated in male, gray pollinose species with black markings resembling aestuans in appearance

Nerax belfragei (Hine)

(TX OK)

19 Tibiae black along with rest of leg; abdominal segments five to seven in male silvery pollinose (14mm Florida only)

Nerax slossonae (Hine)

(FL)

19  Tibiae partly at least, reddish, yellowish, or brownish; hypopygium most prominent at middle apically, generally larger species

   20

 


 

 

20  Costa more or less dilated in male; usually larger, robust species; mystax black, intermixed with white or yellow hairs; tibiae brownish; female ovipositor 4.5-6 mm long

                                             21

 

20  Costa not dilated, smaller, slenderer species; mystax with black bristles above and pale yellow hairs below; tibiae honey-yellow in part; female ovipositor 4-4.5 mm long

                    22

 

20 Costa not dilated, mystax yellowish; female ovipositor very short at 2-3mm (13-15mm)

Nerax aurimystacea (Hine)

(KS OK TX)

 


 

 

21  Large species, (26-32mm), robust; female tibiae and tarsi dark reddish, ovipositor over 7 mm long 

Nerax femoratus (Macquart)

(SC NC LA FL GA)

21 Smaller species (14-28mm), less robust; tibiae brown, general body color black with contrasting gray pollinose bands and spots; female with tips of the tibiae and tarsi black; ovipositor 6mm

Nerax aestuans (Linnaeus)

(Extensive)

21  Smaller species (15-23), males with dorsum of abdominal segments 2-6 black, sides and posterior margin of abdominal segment 6 white and segment 7 all white; female ovipositor a short 4 to 5mm long, abdominal segment 7 brownish pollinose

Nerax tabescens (Banks)

(FL GA)

 


 

 

22  Apical part of hypopygium narrowed and curved downward, with a tooth-like prominence above, (12-22mm)

 Nerax apicalis (Wiedemann)

(GA TX LA MS AL FL SC NC)

22 Apical part of hypopygium nearly as wide as preceding part; mystax largely straw-yellow (17mm)

Nerax kansensis (Hine)

(KS OK TX)

 


 

 

23  Mesothorax compressed anteriorly and with a conspicuous crest of erect hairs on mid-dorsal line, (Carinefferia/carinatus group)

   24

23 Mesothorax broadly rounded above and without a conspicuous crest of hairs

                                             28

 


 

24  Males, abdomen without long white parted hair; females ovipositor slender, more than 4mm long or shorter than this and tibiae and tarsi reddish

                    25

24 Males, abdomen with long white parted hair on several segments

                                                                                         26

 


 

 

25  Males abdomen wholly grayish pollinose and white haired, scutellar bristles white; females mystax white and ovipositor 4-5mm long

Carinefferia ordwayae (Wilcox)

(AZ NM TX)

25 Males basal part of abdominal segments 2-4 or 2-5 black, at least some black hairs on 4-5; scutellar bristles black; females mystax with some black hairs and ovipositor 5-6mm long

Carinefferia willistoni (Hine)

(AZ CO NM TX UT)

 


 

 

26  Male mystax largely white; wings hyaline; male abdomen with segments 1-7 densely grayish white pollinose, 2-5 with white parted hairs; females ovipositor short 3mm long (13-16mm)

Carinefferia cressoni (Hine)

(NM AZ CO TX WY)

26 Male mystax largely black; wings light brownish; Females ovipositor 3.5-6 mm long

                                                                                                                                      27

 


 

 

27  Mesonotal crest of hairs anteriorly subequal in length to antennal segment 1; discal hairs of scutellum sparse white and shorter than marginal bristles; female ovipositor 5-6 mm long (19-21mm)

Carinefferia willistoni (Hine)

(AZ CO NM TX UT)

27 Mesonotal crest of hairs subequal in length to antennal segments 1-3; discal hairs of scutellum dense white and nearly as long as the marginal bristles; female ovipositor 3.5 mm long, sides of abdominal segments 2-7 gray pollinose (14mm)

Carinefferia costalis (Williston)

(EXT Western & TX KS)

 


 

 

28  Mesothorax with numerous bristly hairs, which are unusually long, scutellum conspicuously hairy and with numerous marginal bristles (Aridefferia/aridus group)

                    29

28 Mesothorax with very short hair anteriorly, a few rather prominent bristles posteriorly; scutellum with short hair on disk and usually with not more than half a dozen bristles on margin

                                                                                                                                      30

 


 

 

29  Mystax straw yellow; male abdominal segments four to seven silvery; females bristles of tibiae and tarsi in part black, femora reddish at tip, scutellar hairs white or yellow (14-24mm)

Aridefferia snowii (Hine)

(KS CO NM TX OK SD)

29 Mystax white; female scutellar hairs black and only 8 in number (16mm)

Aridefferia prattii (Hine)

(TX)

29 Mystax with many black hairs; female basal half or more of tibiae reddish with scutellar hairs white or yellowish and with about 20 bristles

Aridefferia subarida (Bromley)

(AZ NM UT TX)

 

 


 

30  Male with ventral prominences on abdominal segments four, five and six; small slender species, (tuberculatus group)

Tuberculefferia tuberculata (Coquillett)

(TX AZ NM OK CO KS)

30 Male abdomen without ventral prominences (Albibarbefferia/barbatus group)

                                                                                                                                      31

 


 

31  Hypopygium small or of normal size, medium-sized or small species, usually of slender build, male costa not at all or only very slightly expanded, female with each abdominal segment black, with posterior gray border of various widths according to species

                    32

31 Hypopygium distinctly enlarged, large to very large species, male costa rather conspicuously thickened and expanded, female abdomen variously marked, but usually the segments not black with posterior gray border, although sometimes close to this marking

                                                                                                                                      33

31  Hypopygium distinctly enlarged, costa not at all thickened and expanded, mystax straw yellow in both sexes, bristles of thorax and scutellum pale; abdomen uniformly yellowish gray pollinose; male with apical abdominal segments partly or wholly silvery (25-30mm)

Albibarbefferia leucocoma (Williston)

(KS TX OK CO)

 


 

 

32  Mystax pale, sometimes with a few black bristles on upper margin (13-20mm)

Albibarbefferia albibarbis (Macquart)

(Extensive)

32 Mystax largely black with pale hairs and bristles intermixed; five, six and seven segments of male abdomen silvery; pale bands of abdomen silvery, regular and narrow (22mm)

Carinefferia willistoni (Hine)

(AZ CO NM TX UT)

 


 

 

33  Male hind tibiae with an abnormal enlargement on apical half (30-32mm)

Albibarbefferia armata (Hine)

(TX)

33 Male hind tibiae with apical third enlarged (28-30mm)

Albibarbefferia tagax (Williston)

(AZ TX NM)

33  Male hind tibiae normal; male seventh abdominal segment entirely silver dorsally; female fifth abdominal segment not silvery

                    34

 


 

 

34  Wings hyaline; grayish pollinose species (21-26mm)

Albibarbefferia bicolor (Bellardi)

(CA AZ NM TX UT LA MS)

34 Wings brownish, especially apex; disk of scutellum with black instead of white hair, (31-35mm)

Albibarbefferia grandis (Hine)

(TX)