The morphological ontogeny of Nothrus palustris C.L. Koch, 1839 is redescribed and illustrated. The morphology of this species has already been investigated in the last century, but these descriptions were either general or incomplete, and lack some cupules, lateral aspect of some instars, and leg setation, which are necessary for morphological comparisons. In the larva of N. palustris the bothridium is weakly developed and bothridial seta is short, whereas in the nymphs and adult the bothridium is well-developed, and bothridial seta is setiform and very long. In this species one pair of exobothridial setae is present. In all instars most prodorsal setae are short, with thickened ro and le in the larva, and ro, le, and in in the nymphs and adult. Most gastronotal setae are of medium size or short, except for long f₁ and very long h₁ in the larva, and long h₁ and very long h₂ in the nymphs and adult. All setae are finely barbed in the larva, and smooth in the nymphs and adult, and they are usually covered with phylliform cerotegument. In all instars the femora are with reticulate ornamentation, and some leg setae (d, l, ft) are thickened and finely barbed, whereas the other setae are thin and smooth. Formulae of femoral setae (leg I–IV) are 7-7-4-3 in the deutonymph, 8-8-6-5 in the tritonymph, and 8/9-8-6-5 in the adult. The illustrations of N. palustris are supported by SEM images. We also summarised knowledge on the ecology and compared the molecular data (COI) of N. palustris from different locations, based on our own and public data.