Nearctic Dicranota (Rhaphidolabis) species

Dicranota Zetterstedt, 1838: 851

The genus Dicranota is divided into 11 subgenera and includes about 280 species worldwide (Oosterbroek 2017).  These include some of the smallest members of the family Pediciinae (Alexander 1967). The Nearctic fauna is comprised of 73 species placed in seven subgenera; Dicranota (15), Eudicranota (4), Paradicranota (4), Plectromyia (15), Polyangaeus (3), Rhaphidolabina (1), Rhaphidolabis (31).  The subgenera were erected based on differences in wing venation, although there have been no phylogenetic studies aimed at testing the monophyly of either Dicranota or the included subgenera.  Rhaphidolabis, the largest subgenus, seems to have a classic East/West split distribution, with seven species east of the Mississippi and the remaining 24 in the Western US. Alexander's (1967) treatment of the crane flies of California included a key to about 20 of the western species. Several species were excluded either because they were known only from females or were considered subspecies at the time.  The updated key below includes all species west of the Mississippi, along with images from Alexander's descriptions (Alexander 1949, 1954, 1967).  

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Key to the Western Species of Dicranota (Rhiphidolabis)

1.  General coloration of body yellow; male hypopygium with tergal arms produced caudad into long slender      spines (Fig. 1)...xanthosoma Alexander, 1944. ​USA (Wash, Oreg).​
-    General coloration of body brown or gray; male hypopygium not as above...2

Figure 1. Male terminalia of D. xanthosoma, from Alexander (1954)

Figure 2. Male terminalia of D. polymeroides, from Alexander (1954)

Figure 3. Wing of D. polymeroides, from Alexander (1967)

2.  Antennae of male elongate, exceeding one-half the wing or extending to beyond base of abdomen; male
     hypopygium with posterior margin of tergite including broad obtuse lateral lobes and slender​    
   intermediate lobules that are separated by a broad U-shaped emargination (Fig. 2); venation (Fig. 3)......
     ...polymeroides (Alexander, 1914). USA (Alaska, Wash, Idaho, south to Calif). 
-   Antennae of male short, not extending to the wing root; male hypopygium with tergite not as above...3

3.  Wings with Sc short, Sc1 ending opposite or before fork of Rs (e.g., Fig. 4)...4
-    Wings with Sc longer, Sc1 ending some distance beyond fork of Rs, usually opposite or beyond the fork of
     R2+3+4...10

4. Wings with r-m ending before the fork of Rs, the latter very strongly arcuated, R2+3+4 short, suberect
​    (Fig. 4)...tehama Alexander, 1950. USA (Calif).
-  Wings with r-m at or beyond fork of Rs, the latter relatively long, angulated and in cases short-spurred
   beyond origin (e.g., Fig. 5)...5

Figure 4. Wing of D. tehama, from Alexander (1967)

Figure 5. Wing of D. nuptualis, from Alexander (1967)

5.  Wings with cell R3 petiolate; male hypopygium with tergal region not produced into lateral arms, the
     median region of posterior border with a small circular emargination behind which is a darkened area
     that bears numerous setae; basistyle without a modified arm on mesal face near apex (Fig. 6).............
​     ...fenderi Alexander, 1954. USA (Oreg).
-    Wings with cell R3 sessile; male hypopygium with posterior border of tergite broadly emarginate, the
     sides with pale strong arms (e.g., Fig. 7); basistyle on mesal face near apex with a short to longer pale
     arm that terminates in a blackened spine or elongate blackened blade, or else in a microscopic pale point
​     (Fig. 8)...nooksackensis group, 6

Figure 6. Male terminalia of D. fenderi, from Alexander (1954)

Figure 7. Male terminalia of D. uniplagia, from Alexander (1954)

Figure 8. Outer lobe of basistyle of Dicranota (Rhaphidolabis) spp; A, nook- sackensis; B, brevispinosa; C, denningi; D, evanescens; E, brevicula Alexander

6.  Apical arm of basistyle very short, terminating in a longer strong blackened acute spine (Fig. 8A).......
     ...nooksackensis Alexander, 1949. Canada, USA (Alaska, south to Oreg and Calif).
-    Apical arm of basistyle longer, the pale base subequal to or longer than darkened outer part...7

7.  Apical arm of basistyle stout, terminating in a microscopic pale point (Fig. 8E)....................................
   ...brevicula Alexander, 1966. USA (Calif).
-   Apical arm of basistyle terminating in a blackened blade or spot (Fig. 8B-D)...8

8.  Apical arm of basistyle long and slender, terminating in a short blackened spinelike point that is
​     extended farther into a paler setoid prolongation (Fig. 8B)...brevispinosa Alexander, 1958. USA (Wash).
-    Apical arm of basistyle shorter, terminating in a blackened blade, the apex obtuse...9

9.  Apical arm of basistyle with the blackened apex longer, only slightly less than the pale basal stem
     (Fig 8C)...denningi Alexander, 1966. USA (Calif).
-    Apical arm of basistyle with the blackened apex relatively short, slightly more than one-half the pale
     basal stem (Fig. 8D)...evanescens Alexander, 1966. USA (Calif).

10.  Wings with cell R3 sessile or subsessile, in the latter case (subsessilis) with R2+3+4 shorter than basal
       section of Rs, the latter equal to r-m (Figs. 9, 10)...11, sessilis (Alexander, 1917), USA (Colo), known
       from a single female, keys here. 
-      Wings with cell R3 petiolate (Fig. 5)...16

Figure 9. Wing of D. vanduzeei, from Alexander (1967)

Figure 10. Wing of D. subsessilis, from Alexander (1967)

11.  Male hypopygium (Fig. 11) with posterior border of ninth tergite broadly emarginate...12
-      Male hypopygium (Figs. 12-14) with median region of posterior border of tergite slightly produced or
       truncate, not emarginate...13

Figure 11. Male terminalia of D. santaeluciae, from Alexander (1967)

Figure 13. Male terminalia of D. subsessilis, from Alexander (1967)

Figure 12. Male terminalia of D. trichopygia, from Alexander (1967)

Figure 14. Male terminalia of D. vanduzeei, from Alexander (1967)

12.  Size large (wing of 8 about 10 mm); wings with a brown cloud over r-m; basal section of vein Rs
       present, nearly as long as r-m; male hypopygium with the median emargination broad, the lobes
​       divergent (Fig. 7)...uniplagia Alexander, 1954. USA (Oreg).  While the wing was not drawn or described,
       the large body size and structure of the male hypopygium (Fig. 19), would place stigma 
       (Alexander, 1924). USA (Wash, south to Colo), near this species.  This may be incorrect if R3 is not
       sessile.
-      Size smaller (wing of 8 about 8 mm); wings without a darkened cloud over r-m; basal section of vein
       Rs obliterated, r-m at the fork of R4+5; male hypopygium (Fig. 11) with the median emargination
       the lobes less divergent...sanctaeluciae Alexander, 1964. USA (Calif).

13.  Male hypopygium with median region of posterior border of tergite and mesal face of basistyle
       with unusually long setae (Fig. 12)...trichopyga Alexander, 1966. USA (Calif).
​-      Male hypopygium (figs. 311,313) without unusually long setae on the tergite or basistyle
       (Figs, 14, 15)...14

​14.  Wings milky white, without stigmal darkening, veins pale (Fig. 10); male hypopygium with interbase
​        a long swordlike blade; tergite without lateral arms (Figure 13).......................................................
        ...subsessilis (Alexander, 1921). Canada, USA (BC to Mont and Wyo, south to Calif).  
-     Wings with stigmal darkening more evident, veins darker; male hypopygium with interbase short,
      tip bispinous; lateral tergal arm present, their tips obtuse (Fig. 14)...15

​15.  Wings with stigma faint to scarcely &dent, in cases pale brown.......................................................
       ...cayuga (Alexander, 1916). Canada, USA (Alaska to Nfld, south to Oreg, Colo and SC).
-     Wings with stigma conspicuous, brown to dark brown (Fig. 9); male hypopygium (Fig. 14)..............
​      ...vanduzeei (Alexander, 1930). USA (Calif).

16.  Wings faintly suffused with brown, the stigma barely evident; R2+3+4 subequal to r-m (Fig. 5).....
​       ...nuptialis Alexander, 1948. USA (Calif).
-      Wings more whitened, stigma usually conspicuous; R2+3+4 slightly longer than r-m...17

17.  Male hypopygium (Fig. 15) with basistyle produced into a single apical lobe, on its face with a slender
       lobule tipped with blackened spinoid setae; tergite with median region of posterior border produced
       into a conspicuous lobe that is weakly dilated a t outer end, the posterior border virtually truncate or
       very feebly emarginate...integriloba Alexander, 1943. USA (Wash and Idaho, south to Calif and Colo).
-     Male hypopygium (Figs. 16-18) with basistyle produced into two separated apical lobes;
      tergite with median region only slightly produced, the extreme in querula where the lobe is relatively
       short, the sides parallel​...26

Figure 15. Male terminalia of D. intrgriloba, from Alexander (1967)

Figure 16. Male terminalia of D. querula, from Alexander (1967)

Figure 17. Male terminalia of D. neomexicana, from Alexander (1967)

Figure 18. Male terminalia of D. cazieriana, from Alexander (1967)

18.  Wings with stigmal darkening very faint; male hypopygium with median region of tergite produced into
       a parallel-sided lobe; apex of dististyle narrowed into a slender lobe (Fig. 16)........................................
    ...querula Alexander, 1944. USA (Oreg, Idaho, Utah and Calif).
​-      Wings with stigmal darkening conspicuous; male hypopygium with median region of tergite convexly
       rounded; dististyle not narrowed at apex...19

19.  Male hypopygium with lateral tergal lobes short and broad, the apical point short (Fig. 17)..................
​       ...neomexicana (Alexander, 1912). Canada, USA (Alaska, south to Calif, Ariz, NMex and Colo).  A former
       subspecies, subtruncata Alexander, 1949. USA (Wash), would key here.  This species isn't illustrated but
       Alexander's description states "the ninth tergite virtually truncate, the margin at this point very slightly
       convex and with a concentration of setae.  Two or three setae at the apex of the dististyle long and
       conspicuous."  It should otherwise conform to D. neomexicana (Fig. 308).
-      Male hypopygium with lateral tergal lobes relatively narrow, extended into a long terminal spine
       (Fig. 18)...cazieriana Alexander, 1944. USA (Oreg, Calif and Utah).​

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Figure 19. Male terminalia of D. stigma, from Alexander (1949)

An additional species, Dicranota major (Alexander, 1917), is known only from a single female (USA: Colo) and isn't able to be placed in the key.  This is a very large taxon, the largest in the genus according to Alexander (1917).  There are no illustrations but crossvein r is removed from R1.

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Eastern Species (not included in key)
Dicranota (Rhaphidolabis) avis (Alexander, 1926). USA (Maine, south to NC).
Dicranota (Rhaphidolabis) forceps (Alexander, 1924). Canada, USA (Mich to NSc, south to Tenn).
Dicranota (Rhaphidolabis) hickmanae Alexander, 1940. USA (Tenn).
Dicranota (Rhaphidolabis) persimilis (Alexander, 1920). USA (Pa and Md, south to Tenn and SC).
Dicranota (Rhaphidolabis) rogersiana (Alexander, 1925). Canada, USA (Mich, Que).
Dicranota (Rhaphidolabis) rubescens (Alexander, 1916). Canada, USA (Que to NSc, south to NY and Mass).
Dicranota (Rhaphidolabis) tenuipes (Osten Sacken, 1869). Canada, USA (Mich to NBr, south to Md and Va).