The ecology and life histories of odonates were studied in a headwater, sand-bottomed coastal plain stream in Virginia. Quantitative sampling of odonates in sand and silt sediments, on submerged snags and in debris dams was conducted monthly for 13 mo. Six species of odonates were common in the stream. Calopteryx maculata (Calopterygidae) had a univoltine life history, whereas Boyeria vinosa (Aeshnidae) Cordulegaster maculata (Cordulegastridae), Gomphus cavillaris, Hagenius brevistylus and Progomphus obscurus (Gomphidae) were semivoltine. The odonates were most abundant in debris dams, less abundant in silt and sand sediments and least abundant on snags. Habitat-specific production of odonates was 1.3 g m−2 y−1 in debris dams and 0.1 − 0.3 g m−2 y−1 in the sand, silt and snag habitats. The production to biomass ratio (P/B) for Calopteryx was 5.9, whereas ratios for semivoltine species ranged from 2.0 − 4.0.
Analysis of overlap in the use of habitat, food and time showed that greatest ecological separation of the species was in their different use of habitat. Boyeria vinosa and Calopteryx maculata primarily inhabited debris dams, Hagenius brevistylus and Gomphus cavillaris were most abundant in silt and Progomphus obscurus was found almost exclusively in sand. Cordulegaster maculata occurred throughout the stream except on snags. Narrow niche breadths for B. vinosa, C. maculata and P. obscurus based on their use of habitat suggest high fidelity of these species to one habitat, whereas Cordulegaster maculata, with the broadest habitat niche breadth, was a habitat generalist. There was little difference among the species in prey items. Trophic niche breadths of all species were broad, all species feeding on a wide variety of invertebrates, in particular Chironomidae, Ephemeroptera and Plecoptera. Little ecological separation of the species occurred based on their use of time, all species occurring in the stream throughout the year with little staggering of life history events or growth patterns. Seasonal patterns of changing resource availability and the dynamic nature of the stream environment likely are important in regulating the distribution, abundance and interactions of the odonate community in this stream.