Thermal thresholds of the predatory miteBalaustium hernandezi.
The lower and upper thermal activity thresholds of adult and larvalBalaustium hernandezivon Heyden (Acari: Erythraeidae) are compared with those of its preyTetranychus urticaeKoch (Acari: Tetranychidae). Adult femaleB. hernandeziretain ambulatory function (CTmin) and movement of appendages (chill coma) at significantly lower temperatures (5.9 and -2.1 °C, respectively) than those of larvalB. hernandezi(8.1 and -1.7 °C) andT. urticae(10.6 and 10.3 °C). There is no significant difference between the temperature at which adult and larvalB. hernandeziandT. urticaecease walking as the temperature is raised (CTmax) (46.7, 46.3 and 47.3 °C, respectively). However, both life stages ofB. hernandezicease movement (heat coma) below the upper locomotory limits ofT. urticae(46.8, 46.7 and 48.7 °C, respectively). AdultB. hernandezihave significantly faster walking speeds than larvae andT. urticaeacross a range of temperatures. The lower thermal activity threshold data indicate thatB. hernandeziwould make an effective biological control agent in temperate climates; however, the extent of the low temperature tolerances of the species suggests the potential to establish in a northern European climate.
School of Biosciences, University of Birmingham Edgbaston, U.K.
Megan R
MR
Coombs
School of Biosciences, University of Birmingham Edgbaston, U.K.
Jeffrey S
JS
Bale
Balaustium hernandezi; CTmax; CTmin; biological control; chill coma; heat coma