Key to species of Clystopsenella Kieffer

1. Head longer than its maximum width; frontal line indicated as deep sulcus extending from clypeus to anterior ocellus; fore wing membrane with distinct dark spots around apex of radial and marginal cells; distal margin of pterostigma, within marginal cell, straight (early-Miocene Dominican amber)................................................. † C. mirabilis Engel

- Head shorter than its maximum width; frontal line indicated as deep sulcus only near level of antennal foramina; fore wing mostly hyaline, membrane only with yellowish translucent band across region of pterostigma; distal margin of pterostigma, within marginal cell, outcurved (extant fauna).............................................................. 2

2. Occipital carina weakly indicated laterally; medial portion of clypeus forming short lobe, its anterior margin incurved; sublateral tooth of clypeus small, less prominent than lateral acetabular lobe; medial elevation of sternum V low and lacking bare triangular declivity; coxae, trochanters and femora mostly brown and tibiae and tarsi light reddish brown (Australia)................................................................................. C. australiana Lepeco & Melo

- Occipital carina completely absent; clypeus very short, lacking medial lobe (except in males of C. longiventris, which have a short lobe); sublateral tooth of clypeus well developed, more prominent than lateral acetabular lobe; medial elevation of sternum V distinctly pronounced and with bare triangular declivity; legs entirely light reddish brown or yellowish (South America and continental Central America)........................................................................ 3

3. Frons sparsely punctate, punctures on surface between eye and median line with interspaces exceeding diameter of anterior ocellus, becoming denser near antennal foramina; mesoscutum sparsely punctate between notauli, distance between punctures exceeding diameter of anterior ocellus; mesepisternum slightly depressed dorsad of mesepisternal pit; antennae with homogeneous dark brown coloration (South America and continental Central America).................. C. longiventris Kieffer

- Frons densely punctate, punctures on surface between eye and median line with interspaces not exceeding diameter of anterior ocellus; mesoscutum densely punctate between notauli, distance between punctures not exceeding diameter of anterior ocellus; mesepisternum not depressed dorsad of mesepisternal pit, posteriorly with shallow sulcus between pit and posterior edge of sclerite; scape and pedicel yellowish, flagellum light brown (western Costa Rica)................... C. pacifica sp. nov.