1      Vertex of head convex, tumid

2

-       Vertex of head flat

7

2(1)  Cicatrices and often neighboring areas of pronotum contrastingly darker the rest of pronotum

3

-       Cicatrices concolorous with dorsum

4

3(2)   Connexival segments unicolorous (southwestern U.S. and northern Mexico)

contaminatus (Uhler)

-        Connexival segments with contrasting dark margins (New Mexico to Utah

4(2)   Anterolateral pronotal margin thick; head elongate (southwestern U.S.)

-        Anterolateral margins of pronotum thin, compressed; head length about equal to width

5(4)   Head, pronotum, and pleura devoid of dark punctations (western Canada to Baja California)

-        Head, pronotum, and pleura with numerous dark punctations

6(5)   Lateral flange of pygophoral margin acuminate and notched (southern Mexico, Guatemala)

-       Lateral flange of pygophoral margin obtuse, lacking notch (northern Mexico, southwestern U.S.)

7(1)  Venation of hemelytral membrane reticulate (southwestern U.S. and northwestern Mexico)

-       Venation of hemelytral membrane simple

8(7)  Legs with conspicuous black spots (southwestern Mexico)

-       Legs immaculate

9(8)   Spiracles surrounded by a broad dark spot (southeastern U.S.)

-        Spiracles concolorous with venter or narrowly margined in black

10(9) Base of abdomen without tubercle (a weak prominence in some females)

-        Base of abdomen with distinct, forwardly directed tubercle

11(10) Margins of juga denticulate (southern Mexico)

-          Margins of juga without teeth

12(11) Pygophore with pair of small, black teeth at base of medial emargination (southern Mexico)

-          Pygophore without black teeth on posterior surface (most of U.S., northern Mexico)

13(10) Head distinctly wider than long (southern Mexico)

-          Head longer than wide or about equal to length

14(13) Anterolateral pronotal margins distinctly paler than pronotal disc (most of U.S. and northern Mexico)

-          Anterolateral pronotal margins darkened or concolorous with disc

15(14) Anterolateral pronotal margins nearly straight; spiracles at most thinly ringed with black (southwestern U.S. and northern Mexico)

-         Anterolateral pronotal margins distinctly concave; spiracles usually black (central Mexico)