Key to species groups of the genus Trechosia

1 Internal sack armed with multiple spines, penultimate and antepenultimate spines enlarged, elytral microsculpture isodiametric or slightly transverse, elytral striae 1–3 not deeply impressed ........................ ........................................................................................................................................ T. intermedia group

- Internal sack with single copulatory piece or copulatory piece absent, elytral microsculpture strongly transverse, elytral striae 1–3 deeply impressed ........................................................................................... 2

2 Posterior discal setiferous puncture on elytra in the 3rd stria ........................................... T. monticola group

- Posterior discal setiferous puncture on elytra in the 3rd interstria ....................................... T. solutilis group