Natuurtijdschriften

Toegang tot tijdschriften over de Nederlandse natuur

The larvae of Cordulegaster are generally found in the pools of streams where they lie in ambush, buried in the substrate, awaiting unsuspecting prey. J.G. NEEDHAM & H.B. HEYWOOD (1929, A handbook of the dragonflies of North America, Thomas, Springfield) suggest that they prefer largeprey such as subyearling brook trout ( (Salvelinus fontinalis) which may be as large as the larva itself. During September of 1980 C. maculata larvae were collected from Trucka Brook in Essex County. New York. Trucka Brook, a small low gradient stream with sand, gravel and muck bottom is located in the central Adirondack Mountains. On the day collections were made, water temperatures ranged from 8.0 to 11 5°C. A total of 62 larvae were collected in 12 standard Surber collections. Six samples were taken at 06,00 hours EST on 20-IX-80 and six more at 18,00 hours EST on the same date in order to represent both nocturnal and diurnal feeding by the larvae. The Surbers samples were preserved in 5% formalin in the field and later were sorted, identified and stored in 70% isopropanol. The contribution of each invertebrate taxa in the environment (Surber samples) and in the diet of C. maculata was determined on a percentage dry weight basis. Larval anisopterans were identified using the keys of NEEDHAM & HEYWOOD (cf. above) and J.G. NEEDHAM & M.J. WESTFALL(1955, A manual of the dragonflies of North America, Univ. California Press, Berkeley).