Anax imperator Leach, 1815
Common name: Emperor
Preferred environment: well-vegetated mesotrophic to eutrophic lowland lakes and ponds. Also canals and flooded disused gravel pits.
Flight period: early June to late August, exceptionally to late September.
Adult habitat and habits: males are territorial and spend a lot of time patrolling 2-3m above the water body. Will chase off potential competitors and other large hawkers. Copulation occurs away from water in vegetation. Ovipositing females fly with drooped abdomen to deter males.
Oviposition site and behaviour: females oviposit alone placing eggs into the tissues of submerged plants often far from shore. Females make rapid high flights between egg-laying sites.
Larval habitat and habits: eggs hatch after three weeks. Larvae live amongst water plants. In Britain most larvae take two years to complete development, but a small proportion will complete development in a year. In the two-year cycle the last instar larva overwinter in diapause and these emerge synchronously in early summer. One-year cycle larvae will emerge later in summer.
Emergence behaviour: larvae emerge synchronously. Emergence occurs overnight starting early dusk with first flight by dawn. Emergence occurs on any emergent vegetation. At high densities larvae may perch on others.
Range: southern and central Europe north to southern Sweden; Middle East and Central Asia; much of northern and southern Africa including Madagascar.
Determination of adults: species is keyed and male abdominal appendages are figured in Askew (1988). Mature adults are illustrated in colour in Askew (1988) and Brooks (1997).
Determination of larvae: larva is keyed and figured in Askew (1988). Photograph of mature larva is given in Brooks (1997).
|Nelson, B., Thompson, R. & Morrow, C., 2000 (August 01). [In] DragonflyIreland http://www.ulstermuseum.org.uk/dragonflyireland/|