The insect order Odonata is an old insect order having evolved in thePennsylvannian and dominated in the Permian. Today, there are about5,000 species grouped into three extant suborders: Zygoptera -damselflies (Figure 1); Anisoptera - dragonflies (Figure 2); andAnisozygoptera, a small suborder of two Asian species morphologicallyintermediate to the former two groups. Two of the world's threesuborders - Anisoptera and Zygoptera - are found in Michigan.
Distinguishing between the two suborders israther easy, based on body shape and posterior abdominal featuresmentioned in the key below. Both the larvae and adults of all Odonataare carnivores. Larvae of almost all species are aquatic, respiringby means of gills (internal with Anisopera, external with Zygoptera,the later that may also cutaneously respire). The modified labium,used by all larval odonates to capture food, characterizes the larvalstage of this order from from all other insects. It is heldunderneath the head, and, when prey is detected, thrusted out in alightning-like strike. Prey is then seized with palpal lobes at theend of the labium, brought to the mouth and finally macerated withthe larva's mandibles.
1a. Bodyslender, head wider than thorax and abdomen (Figure 1a1); abdomenterminating in three caudal lamellae (gills) (Figure 1a2 and 1a3) -
Fig. 1a2: Ibid., (6x, lateral view).
Fig. 1a3: Ibid., (12.5x, dorsal view).
1b. Bodystout, head usually narrower than thorax and abdomen (Figure 1b1);abdomen terminating in 5 short, stiff, pointed appendages (Figure1b2) -
Fig. 1b2: Erpetogomphusdesignatus larva, (6x, dorsalview). Dark spots on the epiproct are tubucles that normally developon maturing male larvae, and are particularly evident on larvae ofGomphidae, Aeshnidae, Corduliidae and Macromiidae as well as someLibellulidae.