Natuurtijdschriften

Toegang tot tijdschriften over de Nederlandse natuur

Mortality during emergence was studied at an open drain in the city of Nagpur (central India). The total mortality rate (MR) was 10.92% (n = 686). Failure to moult (incomplete emergence state, MR = 4.8%) and failure to expand abdomen and harden wings for flight (complete emergence state, MR = 6.12%) were the two major reasons of mortality. The emerging dragonflies failed to moult and were found dead in the following conditions: cuticle of the thorax split and head and thorax of the pharate partly out of the exuviae (MR = 2.04%), head, thorax and wings out but the entire abdomen trapped in the exuviae (MR = 2.76%). After complete moulting some pharates were found floating, dead or completely exhausted in the water body. Some of the dead pharates had a curved telescopic abdomen and crumpled (MR = 0.44%), or stretched wings (MR = 2.33%), while others exhibited a straight, expanded abdomen and stretched overlapping (MR = 1.75%) or stretched spread wings (MR = 1.60%). Death due to overcrowding and predation was negligible. Statistical analysis revealed that mortality is independent of stage of emergence (P = 0.25).