Behavioural Response and Predation Efficiency of Generalist Predator, <i>Chrysoperla carnea</i> (Stephens) (Neuroptera: Chrysopidae) Larvae to Different Webbing Densities of <i>Tetranychus urticae</i> Koch (Acari: Tetranychidae)

ABSTRACT The present study aimed to investigate the behavioural response, predation rate and feeding time of different larval instars of the insect generalist predator, Chrysoperla carnea (Stephens), towards two webbing densities constructed by the two‐spotted spider mite, Tetranychus urticae Koch, on Solanum melongena . The behavioural responses of three larval instars of the predator were recorded during the first hour after release. All the larvae exhibited similar web‐coping behaviour, that is, web interaction ( WIn ), making entry holes in the silken web threads by inserting their long, pincer‐like mandibles. The entry holes were widened by a short horizontal head‐sweeping movement, coupled with a to‐and‐fro body movement. In both the low (LWD) and high (HWD) webbing density treatments, all instars spent maximum mean time exhibiting ‘searching’ behaviour ( S ). Between the two attack behavioural categories, ‘patrolling’ ( P ) and ( WIn ), the 1st instar larvae spent more mean time in ‘ P ’ behaviour in both LWD (13.44 ± 3.48 min) and HWD (12.45 ± 3.30 min) treatments. While the 2nd instar spent more mean time in ‘ WIn ’ under HWD (9.26 ± 7.07 min) than in ‘ P ’ (5.85 ± 2.37 min). In contrast, the 3rd instar larvae exhibited less frequent ‘ P ’ behaviour under HWD (6.49 ± 2.80 min). Overall, the mean time spent by each instar in resting ‘ R ’ behaviour was found comparatively more under LWD than in HWD. The predation rate of the 2nd instar feeding on T. urticae motiles and eggs was significantly different across each webbing density treatment. After 24 h of release, the larvae preyed more on T. urticae eggs across both webbing densities. These findings suggest that C. carnea 2nd instar should be released at the time of initial establishment of the spider mite colony, that is, at low webbing density, on the host substrate for effective biological control. Furthermore, future bioecological research on insect and mite predators against silk‐producing spider mites should also be conducted under the webbing effect.