FIGURE 4. Heads of US Syzeton species. a–c and e–g, ♂ heads in frontal view. a, Syzeton arizonae n. sp. ♂ holotype from Arizona. b, S. belovi n. sp. ♂ holotype from Texas. c, S. floridanus (Werner, 1990) ♂ from Florida. d, Syzeton pallidus (Werner, 1990) ♂ from Texas. e, S. signatus (Haldeman, 1848) ♂ from South Carolina. f, S. subfasciatus (LeConte, 1855) ♂ from Missouri. Note the difference in interocular space denoted by white double arrows for each species. d and h, ♀ heads in side view. d, S. ater (LeConte, 1875) ♀ from Texas. h, S. ouachitanus (Werner, 1990) ♀ from Mississippi (paratype of Zonantes mississippiensis Werner, 1990). Note the difference in eye size, best seen when comparing the distance from the antennal notch to the edge of the eye, or the space separating the eye from the posterior head margin (white double arrows). Scale bars: 0.1 mm.

Published as part of Gompel, Nicolas, 2022, The genus Syzeton Blackburn, 1891 (Coleoptera, Aderidae) in the United States of America, pp. 243-267 in Zootaxa 5162 (3) on page 264, DOI: 10.11646/zootaxa.5162.3.3, http://zenodo.org/record/6810142