Pictorial key to the ant genera of Illinois
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Fig. 52 Proceratium pergandei (antweb.org)
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Fig. 53 Ponera pennsylvanica (antweb.org)
A Dorsum of mesosoma lacking a promesonotal suture, with the metanotal suture usually lacking as well.
B Tergite of abdominal segment 4 always enlarged and strongly arched so that it forms the rearmost part of the abdomen when viewed in prolife; apex of abdomen directed anteriorly.
...Proceratium
15'
AA Dorsum of mesosoma with at least the promesonotal suture; the metanotal suture usually present as well.
BB Abdominal tergite 4 not strongly enlarged and only weakly arched; apex of abdomen directed rearwards or ventrally not anteriorly.