Morphology-based classification of the flying capacities of aquatic insects: A first attempt

Flight is a key feature of the reproduction and dispersal of emerging aquatic insects. However, morphological measurements of insect flight are mostly available for terrestrial taxa and dragonflies, while aquatic insects have been poorly investigated. We analyzed 7 flight-related morphological parameters of 32 taxa belonging to 5 orders of emerging aquatic insects (Ephemeroptera, Trichoptera, Plecoptera, Diptera, and Megaloptera) with different life history traits related to flight (dispersal strategy, voltinism, adult lifespan, and swarming behavior). After correcting for allometry, we used an a priori-free approach to cluster the individuals according to their flight-related morphology. Then, we explored the levels of agreement between these clusters, taxonomy, and several life history traits of the taxa. All orders were scattered among several clusters, suggesting a large range of flight capacities, particularly for Diptera. We found swarming taxa in each cluster, showing that morphological adaptations to swarming are not identical in all aquatic insects. The clusters did not match the expected dispersal capacity of the taxa as derived from the literature or databases. Heavy wide-winged insects notably gathered taxa traditionally described as good or weak dispersers. Flight capacities based on morphology partly matched with the taxonomy and life-history traits of aquatic insect imagoes. Other parameters such as flight propensity, energy stores, and wing kinematics should help refine their flying and dispersal capacity.