|Onychogomphus forcipatus var. unguiculatus, female|
- Onychogomphus forcipatus var. albotibialis Schmidt, 1954
- Onychogomphus forcipatus var. forcipatus (Linnaeus, 1758)
- Onychogomphus forcipatus var. unguiculatus (Vander Linden, 1820)
These dragonflies usually inhabit clean rivers with a little faster running water and gravel or sandy banks. Occasionally they also occurs at large lakes.
The adults of Onychogomphus forcipatus grow up to 6 centimetres (2.4 in) long, with a wingspan of 5.5–7.5 centimetres (2.2–3.0 in). The eyes of these medium sized dragonflies are widely separated and grey-to-green. The two black lines on the side of the thorax are relatively narrow and touch the midline. It has a yellow line on the vertex and two cells above the anal triangle. The abdomen in males is fitted with three hooks of large size (anal appendages). Cercoids may be dark and have a subterminal tooth. The base of the hindwing is angled in males and rounded in females.
This species is rather similar to Onychogomphus uncatus. The two species can be distinguished on the basis of the shape and extension of the black markings, especially on the thorax and on the last abdominal segments.
Adults can be encountered close to running water and lakes from June through September. In Southern Europe, the emergence period begins in April. After the mating the females lay about 500 eggs into the water. Larvae dug and live buried in the bottom. Their life cycle from egg to imago lasts about 3–5 years.
- Göran Sahlén - Eggshell ultrastructure in Onychogomphus forcipatus unguiculatus (Vander Linden) (Odonata: Gomphidae) - Section of Entomology, Department of Zoology, Uppsala University, Villavägen - International Journal of Insect Morphology and Embryology Volume 24, Issue 3, July 1995, Pages 281-286