Circadian Changes in Susceptibility of Various Species of Gryllidae to Insecticides, Depending on Time of Intoxication and Size of Tested Group

Circadian changes in the susceptibility of adult individuals of three cricket species: field cricket (Gryllus campestris), house cricket (Acheta domesticus), and tropical house cricket (Gryllodes sigillatus) to insecticides belonging to the group of synthetic pyrethroids (Bulldock 025 EC) and oxadiazine (Steward 30 WG) were tested in 2007 and 2008. The assessment included the intoxication of subsequent groups of animals with insecticides at four crucial times of the diurnal cycle – at sunrise, at noon, at sunset, and at midnight. Due to the strongly developed territorial behaviour of Gryllidae, which may strongly affect the results of the analysis, tests were performed both on animals kept separately and on groups of 10 individuals. The application of Steward 30 WG and Bulldock 025 EC caused a significant decrease in the animals’ survival rate to the level of 41% (intoxication at midnight) and 38% (intoxication at sunrise) in G. campestris; 50% (intoxication at sunset) and 61% (intoxication at midnight) in A. domesticus; and 45% (intoxication at midnight) and 50% (intoxication at sunrise) in G. sigillatus, respectively. In the case of G. campestris (the control group) and G. sigillatus (group treated with Bulldock 025 EC) the size of tested groups had a significant influence on their sur-