Key to adult Peltodytes of the U.S. and Canada (Coleoptera: Haliplidae)

Warren U. Brigham
Illinois Natural History Survey
607 East Peabody Drive
Champaign, Illinois 61820

1. Elytron with distinct median callosity; western U.S. and Canada.
   ..............................................Peltodytes callosus (LeConte)
   Elytron without median callosity.
   ........................................................................2

2. Base of head with black collar; north-central and northeastern U.S. and southeastern Canada.
   .............................................Peltodytes edentulus (LeConte)
   Head uniformly pale or nearly so (P. tortulosus may have an infuscate blotch on the vertex).
   ........................................................................3

3. Posterior femur distinctly banded beyond margin of coxal plate.
   ........................................................................4
   Posterior femur uniformly colored beyond margin of coxal plate.
   ........................................................................5

4. Elytron with a large to obscure subhumeral blotch almost on lateral margin (blotch may be reduced to only two punctures connected with black); hind coxal plate "more" angulate; yellow band on hind femur narrow; north-central and northeastern U.S. and southeastern Canada.
   .........................................Peltodytes duodecimpunctatus (Say)
   Elytron without subhumeral blotch; hind coxal plate "less" angulate; yellow band on hind femur broad; north-central and northeastern U.S. and southeastern Canada.
   ...................................................Peltodytes lengi Roberts

5. Posterior femur pale, extreme apex slightly darkened.
   ........................................................................6
   Posterior femur black or dark brown.
   ........................................................................8

6. Sutural area around scutellum broadly concave; basal elytral punctures confluent; pronotal blotches near posterior margin of pronotum usually coalesced across midline; southeastern U.S.
   .................................................Peltodytes dietrichi Young
   Sutural area not concave; basal elytral punctures not confluent; pronotal blotches near posterior margin of pronotum not coalesced across midline.
   ........................................................................7

7. Brightly colored, spots distinct; hind femur yellow; 3.5 mm long; central U.S.
   ..............................................Peltodytes litoralis Matheson
   Dark, spots indistinct; hump-backed; hind femur brownish-yellow; 4.5 to 5 mm long; northern U.S. and Canada.
   ..............................................Peltodytes tortulosus Roberts

8. Elytron typically without subhumeral blotch (some P. sexmaculatus and P. muticus may have a faint blotch).
   ........................................................................9
   Elytron with large to obscure subhumeral blotch.
   ........................................................................13

9. Apex of prosternal process without a distinct margin, although there is a sharp juncture between posterior punctured part and smooth anterior part; California.
   ...............................................Peltodytes simplex (LeConte)
   Apex of prosternal process with a distinct margin or raised carina.
   ........................................................................10

10. Fourth elytral stria complete.
    ........................................................................11
    Fourth elytral stria broadly interrupted.
    ........................................................................12

11. Elytron with all 11 strial rows of blackened punctures; interval between 3rd and 4th strial rows with 3 or 4 extra punctures forming a short row near base of elytron; elytron without coalesced blackened punctures basally, 5th strial row not blackened and impressed basally; 3.5 mm long or less; southwestern U.S.
    ...............................................Peltodytes dispersus Roberts
    Elytron with only 9 strial rows of blackened punctures, the 2 lateral strial rows without dark pigment of any kind; all strial rows complete, except 4th strial row lacking 2nd puncture basally; elytron with "eyebrow-shaped" black mark basally formed by coalescense of blackened basal punctures of strial rows 1 through 4 and 1st 3 punctures of 5th strial row, punctures similarly coalesced, forming a deep groove, especially along 5th strial row; 4.5 to 5 mm long; Oregon County, Missouri.
    ..........................................................Peltodytes n. sp.

12. Elytral punctulation confused posterior to median sutural blotch; median sutural blotches coalescent with sutural stripe; midwest and southern U.S.
    ...............................................Peltodytes muticus (LeConte)
    Elytral punctulation regularly arranged into strial rows; median sutural blotches usually not coalescent with sutural stripe; eastern and southern U.S.
    ............................................Peltodytes sexmaculatus Roberts

13. Sutural stripe evenly narrow, not wider basally than apically; southwestern U.S.
    ................................................Peltodytes festivus Wehncke
    Sutural stripe uneven, occupying most or all of the sutural interval anterior to medial sutural blotch.
    ........................................................................14

14. Last abdominal sternite posteriorly longitudinally rugose; sutural stripe wide anterior to medial sutural blotch, reaching first strial row of punctures throughout entire basal half.
    ........................................................................15
    Last abdominal sternite shining.
    ........................................................................16

15. Posterior coxal plates rounded at apex, scarcely perceptibly angulate; first and second segments of middle tarsus of male strongly produced; eastern U.S.
    ................................................Peltodytes shermani Roberts
    Posterior coxal plates angulate; first and second segments of middle tarsus of male thickened, but scarcely produced; Florida and Georgia.
    ...............................................Peltodytes oppositus Roberts

16. Aedeagus toothed; sutural stripe wide anterior to medial sutural blotch, reaching first strial row of punctures throughout entire basal half.
    ........................................................................17
    Aedeagus not toothed; sutural stripe wide medially, often reaching first strial row of punctures, narrowing basally, only occupying half the sutural interval.
    ........................................................................18

17. Parameres with apical setae; Florida.
    ............................................Peltodytes floridensis Matheson
    Parameres without apical setae; central and southeastern U.S.
    ..................................................Peltodytes dunavani Young

18. Aedeagus undulating; southeastern U.S.
    ..................................................Peltodytes bradleyi Young
    Aedeagus not undulating; central U.S.
    ........................................Peltodytes pedunculatus (Blatchley)