Abstract
The susceptibility (48‐h LC 50 values) of aquatic life stages of Xanthocnemis zealandica McLachlan to azinphos‐methyi and carbaryi was investigated. The LC50 values of azinphos‐methyi did not correlate with instar. The most susceptible stage was instar 7 (LC 50 value: 26.6 ppb), and the least susceptible were instars 2 (LC50 value: 50.2 ppb) and 13 (LC 50 value: 45.1 ppb). In contrast, LC 50 values for carbaryi were positively related to larval instar (instar 2: LC 50 value: 156.6 ppb; instar 13: LC 50 value: 760 ppb). Damselfly eggs were exposed to insecticide solutions (azinphos‐methyi: control, 0.04, 0.4, 4, and 40 ppb; carbaryi: 0.6 b and 6, 60, and 600 ppb) and hatching success evaluated. Only carbaryi at 600 ppb reduced hatching success significantly. Although the investigation on eggs was carried out at a higher temperature than the LC 50 experiments it can be concluded that the egg stage is more resilient to both insecticides than the larval stages.