Key to the Phymatinae of Illinois

1 Size small, length 5–6.5 mm; scutellum with linear or sublinear carina, lateral branches absent or obsolete................................................................................................. Phymata vicina vicina

- Size larger, length larger than 7 mm; scutellum with cruciform carina, lateral branches well-developed................ 2

2 (1') Posterolateral angles of first three connexival segments noticeably protruding and dentiform; lateral margin of fourth connexival segment distinctly curved to sinuate.............................................. Phymata fasciata fasciata

- Posterolateral angles of first three connexival segments more or less straight, at most with small salient angles; lateral margin of fourth connexival segment more-or-less straight.......................................................... 3

3 (2') Fourth connexivum not abruptly dilated, lateral margin near junction of third and fourth connexivum more or less straight, outline of connexival segments 1–3 not smooth, often with small salient angles posterolaterally; male with fourth antennal segment at most subequal in length to second and third combined; size slightly larger, length 8.5–10 mm ............................................................................................... Phymata americana americana

- Fourth connexivum abruptly dilated, lateral margin near junction of third and fourth connexivum distinctly angulate, especially in the males, outline of connexival segments 1–3 entire, smooth, usually without projecting angles posterolaterally; male with fourth antennal segment distinctly longer than second and third combined; size slightly smaller, length 7.5–9 mm ............................................................................................ Phymata pennsylvanica