Key to Trinodia species

This key to the twelve species of Trinodia is based on: [[Media:Potts 1945 key to species cremastocheilini.pdf|Potts, R.W.L. 1945. A key to the species of Cremastocheilini of North American and Mexico (Coleoptera: Scarabaeidae). Bull. Brooklyn Ent. Soc. 40: 72-78.]] and Alpert, Gary D. 1994. A Comparative Study of the Symbiotic Relationship Between Beetles of the Genus Cremastocheilus (Coleoptera: Scarabaeidae) and their Host Ants (Hymenoptera:Formicidae). Sociobiology 25(1).

You may also be interested in: [[Media:Krikken 1981.pdf|Krikken, J. 1982. North American myrmecophilous beetles of the genus Cremastocheilus: discussion of their classification and a review of the subgenera Trinodia and Anatrinodia (Coleoptera: Cetoniidae). Proceedings of the Koninklijke Nederlandse Academie van Wetenschappen. Series C. p. 509-526.]] and [[Media:Mynhardt & Wenzel 2010.pdf|Mynhardt, G. & J.W. Wenzel 2010. Phylogentic analysis of the myrmecophilous Cremastocheilus Knoch (Coleoptera, Scarabaeidae, Cetoniinae), based on external adult morphology. ZooKeys 34: 129-140.]]

1

 * Front of head with a transverse impression in front of eyes; Pronotum only slightly more than one-half as wide as elytra: Arizona (Fig. ) .......Cremastocheilus constricticollis


 * Front of head without a transverse impression in front of eyes; Pronotum at least three-fourths as wide as elytra . . . . . 2

2
return to couplet #1
 * Tarsi 4-segmented, AZ (Fig. ). . . . . Cremastocheilus lengi


 * Tarsi 5-segmented . ... . . . . . 3

3
return to couplet #2
 * Large tuft of trichome hairs on ocular canthus and in depression centrad and adjacent to anterior pronotal angles. Clypeus strongly carinate at middle (Fig. ) AZ, CA, NV, UT...Cremastocheilus opaculus


 * No trichome hairs in a depression centrad and adjacent to anterior pronotal angles ..... . . . . . 4

4
return to couplet #3
 * Posterior tibia notably broad and laterally compressed......... . . . . . 5


 * Posterior tibia not notably broad and laterally compressed..... . . . . . 6

5
return to couplet #4
 * Body black or piceous; moderate excavation inside and anterior to posterior pronotal angles (Fig. ) ..Cremastocheilus planipes


 * Body dark red; posterior angles of pronotum flat above; no excavation inside and anterior to posterior angles ..Cremastocheilus mentalis

6
return to couplet #4
 * Femora not broad and compressed; elytra with elongate punctures, longitudinally connected... . . . . . 7


 * Femora notably broad and compressed; deep sinuation anterior to acutely pointed posterior angles; elytra with punctures separated ... . . . . . 8

7
return to couplet #6
 * Body black above; tomentose areas on head, pronotum, elytra, and under surface, large white tomentose areas on each side of median carina...Cremastocheilus stathamae
 * Body piceous, slightly shining; no tomentose areas on pronotum, no tomentose areas on each side of median carina..Cremastocheilus spinifer

8
return to couplet #6
 * Mentum flat; elytral disc with well-spaced, very slender, narrow, shallow punctures; upper tooth of anterior tibia at about middle of length...Cremastocheilus saucius
 * Mentum somewhat cup-shaped; elytral disc with densely spaced punctures, tooth of anterior tibia beyond middle of length ... . . . . . 9

9
return to couplet #8
 * Body shining; posterior tibia not peductulate; no deep excavation anterior to posterior angles.Cremastocheilus quadricollis and Cremastocheilus setosifrons
 * Body opaque to subopaque; anterior and posterior tibia pedunculate; a deep excavation inside and anterior to each posterior angle... . . . . . 10

10
return to couplet #9
 * Middle and posterior tibia not noticeably compressed; tarsi not rounded; mentum only slightly cup-shaped ..Cremastocheilus hirsutus
 * Middle and posterior tibia compressed; tarsi short, rounded, segments subequal; mentum somewhat cup-shaped..Cremastocheilus excavatus