| Popis: |
The illustrated identification key to the nymphs of the seven Anisoptera families of North America includes traditional distinctions and several new characters. Petaluridae are distinguished primarily by a prominent spiny process on the palpus and four movable spurs on all tibial apices. The Aeshnidae and Gomphidae have a flat labium, distinguishing them from the remaining four families that have a scoop-shaped labium; aeshnids have 6- or 7-segmented antennae, gomphids have 4-segmented antennae. The distal margin of the palpus in Cordulegastridae nymphs has large angular teeth and the ligula has a median bifid process. Macromiidae have mesothoracic femora 1.2–1.6 times the width of the head, compared to the Corduliidae and Libellulidae in which the mesothoracic femora are usually shorter than the head is wide (ratio 0.6–1.0, rarely 1.1). The main character separating the two most difficult families, Corduliidae and Libellulidae, is that Corduliidae nymphs have a definite ventromedial groove on the prementum. Additional diagnostic characters are provided. |
