KEY TO THE SPECIES OF THE GENUS ORCONECTES


NOTE:  In using this key, the first pleopod must be viewed mesially.  For comparative purposes, all of the illustrations of this appendage are made of the left member of the pair.  See Fig. 3c for terminology and methods of measurements.

EDITOR's NOTE:  The genus Orconectes was subdivided into 10 subgenera by Fitzpatrick (1987) and later modified by Bouchard & Bouchard (1995).  To view a table of the breakdown of species in each subgenus, click here.


1.    Central projection of first pleopod constituting 1/4 or less of total length of appendage
        (Fig. 60, 63, 65, 67c-g):..............................................................................................................................  2
  • Central projection of first pleopod constituting more than 1/4 total length of appendage
    (Figs. 68c-g, 70, 72, 74, 77):..................................................................................................................  32

2(1).  Albinistic; eyes without pigment or facets..................................................................................................  3

  • Pigmented; eyes with pigment and facets.................................................................................................  8
Fig. 60.  Mesial view of left first pleopods.  a, Orconectes pellucidus;  b, O. incomptus;  c, O. a. australis;  d, O. a. packardi;  e, O. i. inermis;  f, O. i. testii;  g, O. harrisoni.  (s, shoulder).

3(2).  Mesial process of first pleopod extending distinctly farther distally than central projection
          (Fig. 60a; see also Fig. 11b):.............................................  Orconectes pellucidus  (Tellkampf, 1843).

       (Subterranean waters from Hart County to Trigg County, Kentucky, and Montgomery County,
        Tennessee.  Literature:  Hobbs and Barr, 1972).

  • Mesial process of first pleopod extending only slightly, if at all, farther distally thancentral
    projection (Fig. 60b-f):...........................................................................................................................  4

4(3).  Cephalodistal portion of first pleopod with rounded or angular weak shoulder (s) at base of
          central projection (Fig. 60b-d):.............................................................................................................  5

  • Cephalodistal portion of first pleopod without shoulder at base of central projection (Fig. 60e, f):
    .............................................................................................................................................................  7

5(4).  Rostrum without marginal spines or tubercles (Fig.  61a; see also Fig. 60b): ......................................
          ...........................................................................................  Orconectes incomptus  Hobbs and Barr, 1972.

       (Subterranean waters in Jackson County, Tennessee.  Literature:  Hobbs and Barr, 1972).

  • Rostrum with marginal spines of tubercles (Fig. 61b, c):..........................................................................  6
Fig. 61.  Dorsal view of carapaces.  a, Orconectes incomptus;  b, O. a. australis;  c, O. a. packardi;  d, O. i. inermis;  e, O. i. testii

6(5).  Cephalodistal portion of first pleopod with angular shoulder at base of central projection;
          caudal process absent (Fig. 60d; see also Fig. 61c):......................................................................
          .......................................................................................  Orconectes australis packardi  Rhoades, 1944.

       (Subterranean waters of the upper Cumberland drainage system in Kentucky, intergrading
        with the nominate subspecies in the vicinity of the Kentucky-Tennessee state line.
        Literature:  Hobbs and Barr, 1972).

  • Cephalodistal portion of first pleopod with rounded shoulder at base of central projection;
    caudal process usually present (Fig. 60c; see also Figs. 11a, 61b):.......................................................
    .......................................................................................  Orconectes australis australis  (Rhoades, 1941).

       (Subterranean waters in the northern tributaries of the Tennessee River in Jackson and
        Madison Counties, Alabama, north-northeastward on the Cumberland Plateau to near the
      Kentucky-Tennessee state line, there intergrading with O. a. packardi.  Literature:  Hobbs
        and Barr, 1972).


7(4).   Rostrum with marginal spines or tubercles; areola constituting less than 43 per cent of total
           length of carapace (Fig. 61d; see also Figs. 11c, 60e):..................................................................
           ..........................................................................................  Orconectes inermis inermis  Cope, 1871.

       (Subterranean waters from Green County, Kentucky, to Crawford County, Indiana, intergrading
         with O. i. testii northward to Monroe County, Indiana.  Literature:  Hobbs and Barr, 1972).

  • Rostrum without marginal spines or tubercles; areola constituting at least 43 per cent of total
    length of carapace (Fig. 61e; see also Fig. 60f):...........................  Orconectes inermis testii (Hay, 1891).

       (Subterranean waters of Monroe County, Indiana, intergrading southward to Crawford County
         with the nominate subspecies.  Literature:  Hobbs and Barr, 1972).


8(2).  Central projection of first pleopod constituting less than 1/7 total length of appendage and both terminal elements directed caudodistally (Fig. 60g):...............................................  Orconectes harrisonii  (Faxon, 1884).

       (Streams in St. Genevieve and Washington counties, Missouri.  Literature:
        Creaser, 1934a;  Williams, 1954a).

  • Central projection of first pleopod usually consisting at least 1/6 total length of appendage
    (Figs. 63, 65, 67c-g), if less, then both terminal elements never directed caudodistally (Fig. 65a):........
    .........................................................................................................................................................   9

9(8).  Areola obliterated of linear along part of length (Fig. 62a):...................................................................  10

  • Areola never obliterated along any part of length (Figs. 62b-e, 67a, b):..................................................  13
Fig. 62.  Dorsal view of carapaces.  a, Orconectes lancifer;  b, O. limosus;  c, O. propinquus;  d,  O. eupunctus;  e, O. erichsonianus.

10(9).  Rostrum with acumen as long as, or longer than, basal portion (Fig. 62a):.......................................
            .............................................................................................  Orconectes lancifer  (Hagen, 1870).

       (Lentic and sluggish lotic habitats from Texas and Mississippi northward to extreme
        southern Illinois.  Literature:  Hobbs and Marchand, 1943;  Penn, 1952;  Penn and Hobbs, 1958).

  • Rostrum with acumen never as long as basal potion..........................................................................  11
Fig. 63.  Mesial view of left first pleopods.  a, Orconectes mississippiensis;  b, O. difficilis;  c, O. hathawayi;  d, O. sanborni erismophorous;  e, O. sloanii;  f, O. obscurus;  g, O. immunis,  h, O. marchandi;  i, O. kentuckiensis.

11(10).   Mesial process of first pleopod with basal protion directed distally and distal 1/3 bent caudally
                at right angle to principal axis of appendage (Fig. 63a):..................................................................
                .....................................................................................  Orconectes mississippiensis  (Faxon, 1884).

       (Streams and roadside ditches in eastern in eastern Mississippi and western Alabama.
        Literature:  Faxon, 1884).

  • Mesial process of first pleopod directed caudodistally from base (Fig. 63b, c):.......................................  12

12(11).   Central projection of first pleopod strongly tapering from base to acute apex (Fig. 63b):...
                ..................................................................................................  Orconectes difficilis  (Faxon, 1898).

       (Streams from Latimer and Pittsburg counties, Oklahoma, and Upshur county, Texas, to
        Arkansas and western Louisiana.  Literature:  Penn, 1952;  Reimer, 1968;  Williams, 1954a).

  • Central projection of first pleopod gradually tapering to cleft or shallowly concave apex (Fig. 63c):...
    ............................................................................................................  Orconectes hathawayi  Penn, 1942.

       (Streams from Jackson and Rapides parishes south to Vermilion Parish, Louisiana.
         Literature:  Penn, 1952).


13(9).  Mesial process of first pleopod with accessory lobe on caudal surface (Fig. 63d):.......................
            ......................................................  Orconectes sanbornii erismophorous  Hobbs and Fitzpatrick, 1962.

       (Streams in the Little Kanawha River system, West Virginia, intergrading with the nominate
         subspecies in neighboring streams.  Literature:  Fitzpatrick, 1967a).

  • Mesial process of first pleopod without accessory lobe on caudal surface (Figs. 63e-i, 65, 67c-g):....................................................................................................................................................  14

14(13).  Cephalic surface of first pleopod with prominent angular or subangular shoulder  (Fig. 63f):........
              .............................................................................................................  Orconectes obscurus  (Hagen, 1870).

       (Streams in southeastern Ontario, New York, Pennsylvania, eastern Ohio, and West Virginia,
         northern Virginia, and western Maryland.  Literature:  Crocker, 1957; Crocker and Barr, 1968;
         Fitzpatrick, 1967a;  Ortmann, 1906).

  • Cephalic surface of first pleopod lacking prominent angular shoulder (Figs. 63e, g-i, 65, 67c-g):....................................................................................................................................................   15

15(14).   Central projection of first pleopod inclined caudally throughout length (Fig. 63e, g-i):........................
                .....................................................................................................................................................   16

  • Central projection of first pleopod never inclined caudally throughout length (Figs. 65, 67c-g):....................................................................................................................................................   19

16(15).   Terminal elements of first pleopod with apices directed caudally at angle of 90 degrees to
                principal axis of appendage (Fig. 63g, see also Fig. 5n):...................................................................
                ............................................................................................................  Orconectes immunis  (Hagen, 1870).

       (Lentic and sluggish lotic habitats from New England and Ontario westward to Wyoming and
        southward to Alabama.  Literature:  Crocker and Barr, 1968).

  • Terminal elements of first pleopod bent caudodistally but apices directed at angle distinctly
    less than 90 degrees to principal axis of appendage (Fig. 63e, h, i):.........................................................  17

17(16).  Central projection of first pleopod constituting more than 1/5 total length of appendage and
               tapering gradually from base to apex (Fig. 63h):........................  Orconectes marchandi  Hobbs, 1968.

       (Streams in the Spring River drainage system in Arkansas and Missouri.
         Literature:  Williams, 1954a).

  • Central projection of first pleopod constituting less than 1/5 total length of appendage and
    bladelike (Fig. 63e, i):............................................................................................................................   18

18(17).  Chela strongly pubescent with setae obscuring tubercles on opposable margins of fingers;
               areola with no more than 3 punctations across narrowest part; mesial process of first
               pleopod somewhat flattened and directed more caudally than distally (Fig. 63i):....................
               ..................................................................................................  Orconectes kentuckiensis  Rhoades, 1944.

       (Streams in Crittenden and Union counties, Kentucky, and Hardin County, Illinois.
         Literature:  Rhoades, 1944a).

  • Chela weakly to moderately pubescent but not obscuring tubercles on opposable margins
    of fingers; areola with 4 or more punctations across marrowest part;  mesial process of first
    pleopod subelliptical in cross-section and directed more distally than caudally (Fig. 63e):.................
    .....................................................................................................................  Orconectes sloanii  (Bundy, 1876).

       (Streams in southern Indiana and southwestern Ohio.  Literature:  Eberly, 1955;
         Faxon, 1885;  Rhoades, 1941a).


19(15).   Terminal elements of first pleopod distinctly divergent (Fig. 65a-d):......................................................  20

  • Terminal elements of first pleopod subparallel or convergent distally (Figs. 65e-i, 67c-g):................
    ..............................................................................................................................................................  23

20(19).  Carapace with hepatic spines (spines occasionally abraded in late inter-molt individuals)
               (Fig. 62b; see also Figs 51, 65a):............................................  Orconectes limosus  (Rafinesque, 1817)

       (Streams on the Atlantic slope from Maine to the lower James River in Virginia.
         Literature:  Crocker, 1957;  Ortmann, 1906;  Rhoades, 1962).

  • Carapace without hepatic spines (Fig. 64a, b):..........................................................................................  21

21(20).   Length of mesial margin of palm of chela less than 1/2 length of dactyl  (Fig. 64c; see also
                Figs. 64a, 65b):..............................................................................  Orconectes shoupi  Hobbs, 1948.

       (Streams in the Cumberland drainage system in the vicinity of Nashville.  Literature:
         Hobbs, 1948a;  Rhoades, 1962).

  • Lenght of mesial margin of palm of chela greater than 1/2 length of dactyl (Fig. 64d, e):...................
    .............................................................................................................................................................  22
Fig. 64.  a-b, Dorsal view of carapaces;  c-e, Dorsal view of chelae.  a, Orconectes shoupi,  b, O. indianensis;  c, O. shoupi;  d, O. wrighti;  e, O. indianensis.

22(21).  Chela densely setose dorsally;  in dorsal aspect, setae obscuring most tubercles on
               opposable surfaces of fingers (Fig. 64d; see also Fig. 65c):...............................................................
                .............................................................................................................  Orconectes wrighti  Hobbs, 1948.

       (Streams in the Tennessee River drainage in Hardin County, Tennessee.
         Literature:  Hobbs, 1948b;  Rhoades, 1962).

  • Chela sparingly setose dorsally;  in dorsal aspect, most tubercles on opposable surfaces
    of fingers clearly visible (Fig. 64e; see also Figs. 64b, 65d):......................................................................
    .............................................................................................................  Orconectes indianensis (Hay, 1896).

       (Streams in southern Illinois and Indiana.  Literature:  Eberly, 1955;  Hay, 1896).


23(19).   Rostrum with median carina (Fig. 62c):................................................................................................  24

  • Rostrum without median carina (Fig. 63d, e):..............................................................................................  25

24(23).   Mesial process of first pleopod with acute apex (Fig. 65e; see also Figs. 5m, 62c):............................
................................................................................................................  Orconectes propinquus  (Girard, 1852).

       (Streams and littoral areas of cold lentic habits from Ontario, Quebec and western
         New England southward to Pennsylvania and westward to Illinois and Wisconsin.
         Literature:  Crocker and Barr, 1968; Fitzpatrick, 1967a).

  • Mesial process of first pleopod truncate or spatulate apically (Fig. 67e):....................................................
    ..................................................................................................  Orconectes iowaensis  Fitzpatrick, 1968.

       (Streams in the Mississippi drainage system in eastern Iowa.  Literature:  Fitzpatrick, 1968).

     EDITOR'S NOTE:  This species is no longer recognized !!     (synonym of Orconectes propinquus).


25(23).   Tip of mesial process of first pleopod constituting at least 1/5 total length of appendage
                (Fig. 65f, g):........................................................................................................................................  27

  • Tip of mesial process of first pleopod not extending distally so far as central projection
    (Fig. 67c-g):.................................................................................................................................................  29

26(25).  Central projection of first pleopod constituting at least 1/5 total length of appendage
               (Fig. 65f, g):...........................................................................................................................................  27

  • Central projection of first pleopod constituting less than 1/5 total length of appendage
    (Fig. 65h, i):...................................................................................................................................................  28

27(26).  Dorsal surface of carapace with large, contiguous, deep punctations (Fig. 62d; see also
               Fig. 65f):.................................................................................  Orconectes eupunctus  Williams, 1952.

       (Streams in the Spring River and Eleven Point drainage systems in Arkansas and Missouri.
         Literature:  Williams, 1954a).

       (Streams in the Coosa and Tennessee drainage systems in Alabama, Georgia, Tennessee,
         and Virginia.  Literature:  Fitzpatrick, 1967a).


28(26).   Mesial process of first pleopod twisted and extending slightly farther distally than
                central projection (Fig. 65h; see also Fig. 66b):...............  Orconectes tricuspis  Rhoades, 1944.

       (Streams in the Cumberland drainage system in Lyon, Trigg, and Christian counties Kentucky.
         Literature:  Rhoades, 1944a).

  • Mesial process not twisted and never extending farther distally than central projection
    (Fig. 65i):.....................................................................  Orconectes sanbornii sanbornii  (Faxon, 1884). 

       (Tributaries of the Ohio River in Ohio, northeastern Kentucky, and West Virginia.
         Literature:  Fitzpatrick, 1967a).

Fig. 65.  Mesial view of left first pleopods.  a, Orconectes limosus;  b, O. shoupi;  c, O. wrighti;  d, O. indianensis;  e, O. propinquus;  f, O. eupunctus;  g, O. erichsonianus;  h,  O. tricuspis;  i, O. s. sanborni.

29 (25).   Mesial margin of palm of chela greater than 1/2 length of dactyl (Fig. 66c, d):..............................
                 ................................................................................................................................................................  30

  • Mesial margin of palm of chela as short as, or shorter than, 1/2 length of dactyl (Fig. 66e):..............
    ......................................................................................................................................................................  31
Fig. 66.  Dorsal view of chelae.  a, Orconectes erichsonianus;  b, O. tricuspis;  c, O. rafinesquei;  d, O. virginiensis;  e, O. illinoiensis.

30(29).  Length of areola greater than 5 times its width (Fig. 67a; see also Figs. 66c, 67c):.........................
               .............................................................................................  Orconectes rafinesquei  Rhoades, 1944.

       (Streams in the Rough River drainage in Kentucky.  Literature:  Rhoades).

  • Length of areola not more than 5 times its width (Fig. 67b; see also Figs. 66d67d):............................
    ......................................................................................................  Orconectes virginiensis  Hobbs, 1951.

       (Streams in the Chowan River drainage in North Carolina and Virginia.  Literature: Fitzpatrick, 1967a).


31(29).   Central projection of first pleopod tapering from base to acute apex (Fig. 67f; see also
                Fig. 66e):.................................................................................  Orconectes illinoiensis  Brown, 1956.

       (Streams in southern Illinois .  Literature:  Fitzpatrick, 1967a).

  • Central projection of first pleopod bladelike with truncate or rounded apex (Fig. 67g):............................
    .......................................................................................................  Orconectes bisectus  Rhoades, 1944.

       (Streams in the Crooked Creek drainage in Crittenden County, Kentucky.
         Literature:  Prins and Fitzpatrick, 1965;  Rhoades, 1944a).

Fig. 67.  a-b, Dorsal view of carapaces;  c-g, Mesial view of left first pleopods.  a, Orconectes rafinesquei;  b, O. virginiensis;  c, O. rafinesquei;  d, O. virginiensis;  e, O. iowaensis;  f, O. illinoiensis;  g, O. bisectus.

32(1).   Hooks on ischia of third and fourth pereiopods (Fig. 4c);  mesial process of first pleopod
             broadened and deeply grooved distally (Fig. 68c):..........  Orconectes peruncus  (Creaser, 1931).

       (Streams in the headwaters of the St. Francis River in southeastern Missouri.
         Literature:  Creaser, 1934a;  Williams, 1954a).

  • Hooks on ischia of third pereiopods only (Fig. 4a), except in some populations of O. hylas;
    if present on fourth, mesial process never markedly broadened distally (Figs. 68d-g, 70, 72, 74, 77):............................................................................................................................................................   33
Fig. 68.  a-b, Dorsal view of carapaces;  c-g, Mesial view of left first pleopods.  a, Orconectes leptogonopodus;  b, O. spinosus;  c, O. peruncus;  d, O. putnami;  e, O. leptogonopodus;  f, O. medius;  g, O. spinosus.

33(32).   Central projection of first pleopod constituting at least 1/2 total length of appendage
                (Fig. 68d-g):............................................................................................................................................   34

  • Central projection of first pleopod constituting less than 1/2 total length of appendage
    (Figs. 70, 72, 74, 77):.................................................................................................................................   37

34(33).   Length of mesial margin of palm of chela no more than 1/2 length of dactyl (Fig. 69a;  see also
                Fig. 68d):..................................................................................  Orconectes putnami  (Faxon, 1844).

       (Streams in the Ohio drainage in western Kentucky, southern Indiana (?), and Tennessee (?).
        The limits of the ranges of this species have not been determined.
        Literature:  Ortmann, 1931, treated this species and O. spinosus as synonyms of O. juvenilis.

  • Length of mesial margin of palm of chela greater than 1/2 length of dactyl (Fig. 69b-d):................   35
Fig. 69.  Dorsal view of chelae.  a, Orconectes putnami;  b, O. leptogonopodus;  c, O. medius;  d, O. spinosus.

35(34).   Rostrum with median carina (Fig. 68a; see also Figs. 68e, 69b):.....................................................
               ........................................................................................  Orconectes leptogonopodus  Hobbs, 1948.

       (Streams in the Red River drainage system in Arkansas and eastern Oklahoma.
        Literature:  Fitzpatrick, 1965;  Williams, 1954a).

  • Rostrum without median carina (Fig. 68b):..............................................................................................   36

36(35).  Chela with large prominent punctations dorsally; width of palm greater than 1.4 times length
               of its mesial margin (Fig. 69c; see also Fig. 68f):....................  Orconectes medius  (Faxon, 1885).

       (Streams in the headwaters of the Big and Merames rivers in southeastern Missouri.
         Literature:  Creaser, 1934a;  Williams, 1954a).

  • Chela with fine punctations dorsally; width of palm less than 1.4 times length of its mesial
    margin (Fig. 69d; see also Fig. 68b, g):....................................  Orconectes spinosus  (Bundy, 1877).

       (Streams tributaries of the Coosa, Kanawha (?), and Tennessee rivers in Alabama, Georgia,
         eastern Tennessee, Virginia (?), and West Virginia (?); see statement in couplet 34.
         Literature:  Ortmann, 1931, treated this species and O. putnami as synonyms of O. juvenilis).


37(33).  Both terminal elements of first pleopod curved caudally or caudodistally (Figs. 70, 72):.................   38

  • Mesial process of first pleopod never directed caudally or caudodistally (Figs. 74, 77):.....................   52
Fig. 70.  Mesial view of left first pleopods.  a, Orconectes hobbsi;  b, O. p. palmeri;  c, O. p. creolanus;  d, O. p. longimanus;  e, O. compressus;  f, O. alabamensis;  g, O. quadruncus.

38(37).   Areola obliterated along part of length or so reduced in width as to accommodate no
                punctations in narrowest part (Fig. 71a, b):..........................................................................................   39

  • Areola broad or narrow but always with room for at least one punctation in narrowest part
    (Fig. 71c, d):..................................................................................................................................................   42

39(38).   Areola not obliterated along any part of length (Fig. 71a; see also Fig. 70a):................................
                ..........................................................................................................  Orconectes hobbsi  Penn, 1950.

       (Streams in the Lake Pontchartrain watershed in Louisiana and Mississippi.
         Literature:  Penn, 1952).

  • Areola obliterated along part of length (Fig. 71b):...............................................................................   40
Fig. 71.  Dorsal view of carapaces.  a, Orconectes hobbsi;  b, O. p. palmeri;  c, O. compressus;  d, O. alabamensis.

40(39).   Central projection of first pleopod comprising more than 1/3 total length of appendage
                (Fig. 70b;  see also Fig. 71b):..................................  Orconectes palmeri palmeri  (Faxon, 1884).

       (Streams in the lower Mississippi Valley in western Tennessee, Mississippi, and Louisiana,
         and in eastern Missouri and Arkansas. 
         Literature:  Penn, 1957).

  • Central projection of first pleopod comprising less than 1/3 total length of appendage
    (Fig. 70c, d):...........................................................................................................................................   41

41(40).   First pleopod with weak shoulder on cephalic surface at base of central projection
               (Fig. 70c):...............................................................  Orconectes palmeri creolanus (Creaser, 1933).

       (Streams in the Lake Pontchartrain watershed and he Pearl and Pascagoula river systems in
        Louisiana and Mississippi.
        Literature:  Penn, 1957).

  • First pleopod with no trace of shoulder on cephalic surface at base of central projection
    (Fig. 70d):....................................................................  Orconectes palmeri longimanus (Faxon, 1898).

       (Western stream tributaries of the Mississippi River from the Arkansas River to the Gulf of
        Mexico, and streams westward to the Guadelupe River Texas.
        Literature:  Penn, 1957).


42(38).  Rostrum with median carina; areola less than 5 time longer than broad (Fig. 71c, d):...................   43

  • Rostrum lacking median carina; areola more than 5 times longer than broad.....................................   44

43(42).   Body strongly compressed laterally (Fig. 71c);  distal portion of central projection of first
               pleopod not strongly recurved (Fig. 70e):.........................  Orconectes compressus  (Faxon, 1884).

       (Streams in the Tennessee, Cumberland, and Barren river systems in Alabama, Kentucky,
         Mississippi, and Tennessee.
         Literature:  Rhoades, 1944a).

  • Body not strongly compressed laterally (Fig. 71d);  distal portion of central projection of first
    pleopod strongly recurved (Fig. 70f):.....................................  Orconectes alabamensis  (Faxon, 1884).

       (Streams in  the Tennessee River system in the vicinity of the Alabama-Mississippi-Tennessee border.
         Literature:  Faxon, 1885).


44(42).  Mesial process of first pleopod with one or more prominences slightly proximal to
               caudodistal extremity (Fig. 70g):...................................  Orconectes quadruncus  (Creaser, 1933).

      (Streams in the headwaters of the St. Francis River in Iron, St. Genevieve, and Madison counties,
       Missouri.  Literature:  Creaser, 1934a;  Williams, 1954a).

  • Mesial process of first pleopod with no prominences slightly proximal to caudodistal
    extremity (Fig. 72):........................................................................................................................................  45
Fig. 72.  Mesial view of left first pleopods.  a, Orconectes rhoadesi;  b, O. validus;  c, O. nais;  d, O. m. meeki;  e, O. m. brevis;  f, O. longidigitus;  g, O. punctimanus;  h, O. virilis

45(44).  Distal 1/4 of mesial process of first pleopod abruptly recurved caudally (Fig. 72a, b):...................  46

  • Distal 1/4 of mesial process of first pleopod not abruptly recurved caudally (Fig. 72c-h):.................   47

46(45).  Principal axis of first pleopod almost straight (Fig. 72a):............  Orconectes rhoadesi  Hobbs, 1949.

       (Stream tributaries of the Cumberland, Duck, and Tennessee rivers in Tennessee.
        Literature:  Hobbs, 1949).

       (Stream tributaries of the Tennessee River in Alabama and southern Tennessee.
         Literature:  Faxon, 1914).


47(45).   Central projection of first pleopod comprising less than 1/3 total length of appendage
                (Fig. 72c, e) (For method of measuring, see Fig. 3c):....................................................................   48

  • Central projection of first pleopod comprising more than 1/3 total length of appendage
    (Fig. 72d, f-h):............................................................................................................................................  49

48(47).  Chela with conspicuous tuft of setae at base of fixed finger and with subserrate rows of
               tubercles on mesial surfaces of palm and dactyl  (Fig. 73a;  see also Fig. 72c):........................
               ...................................................................................................................  Orconectes nais  (Faxon, 1885).

       (Streams in Kansas and Texas eastward to Arkansas; limits of its range not clearly defined
         for apparently often confused with O. virilis.
         Literature:  Creaser and Ortenberger, 1933;  Williams, 1954a;  Williams and Leonard, 1952).

  • Chela without conspicuous tuft of setae at base of fixed finger and tubercles on mesial surfaces
    of palm and dactyl subsquamous (See also Fig. 72e):.......................................................................
    ......................................................................................................  Orconectes meeki brevis  Williams, 1952.

       (Streams in the upper Arkansas River drainage in eastern Oklahoma and norhtwestern Arkansas.
         Literature:  Williams, 1954a).


49(47).  Dactyl of chela approximately 3 times length of mesial margin of palm (Fig. 73x; see also
               Fig. 72f):...............................................................................  Orconectes longidigitus (Faxon, 1898).

       (Tributaries of the White and Little Red rivers in Missouri and Arkansas.
         Literature:  Williams, 1954a).

  • Dactyl of chela distinctly less than 3 times length of mesial margin of palm (Fig. 73b, d, e):.........
    ..................................................................................................................................................................   50

50(49).   Central projection of first pleopod comprising almost 1/2 length of appendage (Fig. 72g;
                see also Fig. 73d):...................................................  Orconectes punctimanus (Creaser, 1933).

       (Streams in the Missouri, St. Francis, and White rivers in Arkansas and Missouri.
        Literature:  Williams, 1954a).

  • Central projection of first pleopod comprising much less than 1/2 length of appendage
    (Fig. 72d, h):...........................................................................................................................................   51

51(50).   Mesial process of first pleopod rather strongly recurved (Fig. 72d); areola constituting less
               than 36 per cent of total length of carapace; tubercles on mesial surfaces of palm and dactyl
               subsquamous (Fig. 73e):................................................  Orconectes meeki meeki  (Faxon, 1898).

       (Streams in the Arkansas, Red, an White river systems in Arkansas.
         Literature:  Williams, 1954a).

  • Mesial process of first pleopod only moderately recurved (Fig. 72h); areola constituting more
    than 36 per cent of total length of carapace;  tubercles on mesial surfaces of palm and dactyl
    distincly elevated (Fig. 73e):.........................................................  Orconectes virilis  (Hagen, 1870).

       (Lentic and lotic habitats in Canada and the northern part of the United States; the southern
         boundry of its range is not known.  Its relationships to O. nais and O. causeyi, the latter here
         considered a synonym, are far from clear.  Introductions into Maryland, California, and perhaps
         elsewhere have resulted in its being one of the most widely dispersed crayfishes in North America.
         Literature:  Crocker and Barr, 1968).


52(37).   Central projection of first pleopod constituting less than 1/3 total length of appendage
                (Fig. 74a-c):.........................................................................................................................................   53

  • Central projection of first pleopod constituting more than 1/3 total length of appendage
    (Figs. 74d-i, 77):.......................................................................................................................................   55

53(52).  Cephalic surface of first pleopod without shoulder at base of central projection (Fig. 74a):..
               ...............................................................................  Orconectes jeffersoni  Rhoades, 1944.

       (Streams in Beargrass Creek drainage in Jefferson County, Kentucky.
         Literature:  Fitzpatrick, 1967a).

  • Cephalic surface of first pleopod with shoulder at base of central projection (Fig. 74b, c):..........
    .................................................................................................................................................................   54
Fig. 73.  Dorsal view of chelae.  a, Orconectes nias;  b, O. m. meeki;  c, O. longidigitus;  d, O. punctimanus;  e, O. virilis.

54(53).   Rostrum with median carina (Fig. 75a); fingers of chela inflated ad gap between them
               greater than 1/4 width of palm (Fig. 75c; see also Fig. 74b):.....................................................
               ..............................................................  Orconectes neglectus chaenodactylus  Williams, 1952.

       (Streams in the North Fork of the White River drainage in Arkansas and Missouri, intergrading
         in the headwaters with the nominate subspecies.
         Literature:  Williams, 1954a, 1954b).

  • Rostrum without median carina (Fig. 75b);  fingers of chela somewhat flattened and gap
    between them less than 1/4 width of palm (Fig. 75d; see also Fig. 74c):...................................
    ..........................................................................................................  Orconectes rusticus  (Girard, 1852).

       (Streams from southern Ontario to Illinois, Ohio, and Kentucky; introduced in New England and
         perhaps elsewhere.  Its relationships to other crayfishes treated by Ortmann, 1931, as
         subspecies are not clear.
         Literature:  Crocker and Barr, 1968;  Rhoades, 1944a;  Ortmann, 1931).


55(52).   Cephalic surface of first pleopod with shoulder or distinct bulge (Figs. 74b s, d-i, 77a-d):..
                ........................................................................................................................................................   56

  • Cephalic surface of first pleopod without shoulder or distinct bulge (Fig. 77e-i):.......................
    .............................................................................................................................................................   68
Fig. 74.  Mesial view of left first pleopods.  a, Orconectes jeffersoni;  b, O. neglectus chaenodactylus;  c, O. rusticus;  d, O. luteus;  e, O. macrus;  f, O. acares;  g, O. nana;  h, O. barrenensis;  i, O. mirus.  (s, shoulder).

56(55).  First pleopods reaching coxae of first pereiopods when abdomen flexed (Fig. 78a):.........
               .......................................................................................................................................................   57

  • First pleopods not reaching coxae of first pereiopods when abdomen flexed (Fig. 78b):.......
    ............................................................................................................................................................  63

57(56).   Areola comprising more than 35 per cent of total length of carapace..................................   58

  • Areola comprising less than 35 per cent of total length of carapace.........................................   59

58(57).   Distal margin of shoulder on cephalic surace of pleopod forming right angle  with base
                of central projection (Fig. 74e):............................................  Orconectes macrus  Williams, 1952.

       Streams in the upper Arkansas  River system in southwestern  Missouri and northwestern
       Arkansas.   Literature:  Williams, 1954a).

  • Distal margin of shoulder on cephalic surface of pleopod distinctly sloping (Fig. 68f;
    see also Fig 69c):...............................................................................  Orconectes medius (Faxon, 1885).

       (See couplet 36 for range and literature).

Fig. 75.  a-b, Dorsal view of carapaces;  c-e, Dorsal view of chelae.  a, Orconectes neglectus chaenodactylus;  b, O. rusticus;  c, O. n, chaenodactylus;  d, O. rusticus;  e, O. luteus.

59(56).   Areola less than 7 times longer than broad...............................................................................  60

  • Areola more than 7 times longer than broad..................................................................................  61

60(59).  Cervical spines well developed (Fig. 68b; see also Figs. 68g, 69d):.................................
               ....................................................................................................  Orconectes spinosus  (Bundy, 1877).

       (See couplet 36 for range and literature).

  • Cervical spines absent or represented by small tubercles (See also Fig. 74f):.....................
    ..........................................................................................................  Orconectes acares  Fitzpatrick, 1965.

       (Streams in the Ouachita drainage system in Arkansas.
        Literature:  Fitzpatrick, 1965).

Fig. 76.  a-c, Dorsal view of chelae;  d-e, Dorsal view of carapaces.  a, Orconectes nana;  b, O. barrenensis;  c, O. mirus;  d, O. barrenensis;  e, O. mirus.

61(59).   Maximum subterminal diameter of mesial process of first pleopod greater than that
                of adjacent segment of central projection  (Fig. 77a):..............  Orconectes hylas (Faxon, 1890).

       (Streams in the Black and Big drainage systems in southeastern Missouri.
         Literature:  Creaser, 1934a;  Williams, 1954a).

  • Maximum subterminal diameter of mesial process of first pleopod less than that of
    adjacent segment of central projection (Fig. 77b, c):....................................................................  62

62(61).    Shoulder on cephalic margin of first pleopod strongly developed; central projection
                 gently curved from base (Fig. 77b):....................................  Orconectes juvenilis  (Hagen, 1870).

       (Streams in the Ohio drainage system in northern Kentucky and in Indiana (?).  The limits of
         the range of this species and the closely allied O. putnami and O. spinosus have not been
         determined.  Literature:  Ortmann, 1931;  latter two treated as synonyms of O. juvenilis).

  • Shoulder on cephalic margin of first pleopod very weakly developed;  central projection
    rather strongly recurved distally (Fig. 77c):.............................  Orconectes ozarkae  Williams, 1952.

       (Streams in the White River drainage system in Missouri and Arkansas.
        Literature:  Williams, 1954a).

Fig. 77.  Mesial view of left first pleopods.  a, Orconectes hylas;  b, O. juvenilis;  c, O. ozarkae;  d, O. menae;  e, O. transfuga;  f, O. williamsi;  g, O. n. neglectus;  h, O. placidus;  i, O. forceps.

63(56).   Lateral margin  of fixed finger of chela bowed;  maximum width of gap between fingers
                greater than 1/4 width of palm (Fig.  75c; see also Figs. 74b, 75a):...........................................
                .............................................................  Orconectes neglectus chaenodactylus  Williams, 1952.

       (See couplet 54 for range and literature).

  • Lateral margin of fixed finger of chela evenly countoured with lateral margin of palm;
    maximum width of gap between fingers usually (except sometimes in O. barrenensis
    and O. mirus) less than 1/4 width of palm (Figs. 75e, 76a-c, 79d):................................................  64

64(63).   Areola comprising more than 35 per cent of total length of carapace......................................  65

  • Areola comprising less than 35 per cent of total length of carapace.............................................  66

65(64).   Rostrum with median carina (Like Fig. 71d) or shallowly excavate (See also Figs. 74d,
               75e):............................................................................................  Orconectes luteus  (Creaser 1933).

       (Stream tributaries of the Marais des Cygnes River, Kansas, eastward to the St. Francis
         River, Missouri and northern Arkansas.  Literature:  Williams, 1954a).

  • Rostrum with narrow, deep, longitudinal excavation between greatly thickened margins
    (See also Figs. 74g, 76a):...............................................................  Orconectes nana  Williams, 1952).
Fig. 78.  Ventral view of thoracic region.  a, Pleopods reaching coxae of first pereiopods (cx1);  b, Pleopods reaching coxae of second pereiopods.

66(64).   Areola more than 6 times longer than broad (Fig.  79c; see also Figs. 77d, 79d):.................
               .....................................................................................................  Orconectes menae  (Creaser, 1933).

       (Streams in the Ouachita River system in Polk and Montgomery counties, Arkansas, and
        the Red River system in Oklahoma.  Literature: Williams, 1954a).

  • Areola less than 6 times longer than broad (Fig. 76d, e):................................................................  67

67(66).   Shoulder on cephalic margin of first pleopod angular (Fig. 74i; see also Fig. 76c, e):.........
                ......................................................................................................  Orconectes mirus  (Ortmann, 1931).

       (Streams in the Elk and Duck drainage systems in Alabama and Tennessee.
         Literature:  Ortmann, 1931).

  • Shoulder on cephalic margin of first pleopod broadly rounded (Fig. 74h; see also Fig. 76b, d):.
    ............................................................................................  Orconectes barrenensis  Rhoades, 1944.

       (Streams in the Barren River drainage in Kentucky and Tennessee and in the Green
        River system in Kentucky.  Literature:  Rhoades, 1944a).


68(55).   Length of dactyl of chela less than twice that of mesial margin of palm (Fig. 80a, b):...........
               ..........................................................................................................................................................  69

  • Length of dactyl of chela greater than twice that of mesial margin of palm (Fig. 80c-e):...........
    ..............................................................................................................................................................  71
Fig. 79.  a-c,  Dorsal view of carapaces.  d,  Dorsal view of chelae.  a, Orconectes transfuga;  b, O. williamsi;  c-d, O. menae.

69(68).   Rostrum with median carina (Fig. 79a; see also Figs. 77e, 80a):........................................
               ...............................................................................................  Orconectes transfuga  Fitzpatrick, 1966.

       EDITOR's NOTE:  This species is no longer recognized.  Synonym of Orconectes neglectus neglectus.

       (Streams in the Rogue River drainage in Jackson County, Oregon.
         Literature:  Fitzpatrick, 1966a).

  • Rostrum without median carina (Fig. 79b, c):.................................................................................  70

70(69).   Areola less than 10 times longer than wide (Fig. 79b; see also Figs. 77f, 80b):................
               .............................................................................................  Orconectes williamsi  Fitzpatrick, 1966.

       (Streams in the headwaters of the White River in Madison County, Arkansas.
        Literature:  Fitzpatrick, 1966b).

  • Areola more than 10 times longer than wide (Fig. 79c; see also Figs. 77d, 79d):...................
    ........................................................................................................  Orconectes menae  (Creaser, 1933).

       (See couplet 66 for range and literature).


71(68).   Length of dactyl of chela greater than 2.5 times length of mesial margin of palm
               (Fig.  80c;  see also Fig. 77h):................................................  Orconectes placidus  (Hagen, 1870).

       (Streams in the Cumberland, Duck, and Tennessee drainage systems in Kentucky,
        Tennessee, and Alabama.  Literature:  Ortmann, 1931).

  • Length of dactyl of chela less than 2.5 times length of mesial margin of palm (Fig. 80d, e):........
    .................................................................................................................................................................  72
Fig. 80.  Dorsal view of chelae.  a, Orconectes transfuga;  b, O. williamsi;  c, O. placidus;  d. O. forceps;  e, O. n. neglectus.

72(71).   Gap between closed fingers of chela more than 1/4  width of palm (Fig. 80d; see also
                Fig.  77i):......................................................................................  Orconectes forceps  (Faxon, 1884).

       (Streams in the Tennessee River system from southwestern Virginia to Alabama.
         Literature:  Ortmann, 1931).

       (Streams in the White, except North Fork, and Arkansas river systems in Missouri, Oklahoma,
         and Arkansas, and in tributaries of the Kansas River in Colorado, Nebraska, and east central
         Kansas.  Literature:  Williams, 1954a, 1954b).


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END OF ORCONECTES

Last Updated:  11 September 2006