Functional response of different larval instars of the green lacewing, Chrysoperla carnea (Neuroptera: Chrysopidae), to the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

The green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), is an important predator of soft-bodied pests such as spider mites throughout the world. The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest in many crop systems such as cotton in many parts of the world. In this study, the functional response of the three larval instars of C carnea was studied on adult females of T urticae in 6-h laboratory experiments. The experiments were performed in Petri dishes (6 cm diameter) lined with a layer of solidified agar solution as a substrate for cotton leaf discs. First and second larval instars of the predator exhibited Type II functional responses against the prey. Third instar larvae of the predator, however, showed Type III functional response. The attack rates (a) and handling times (T-h) of the first and second larval instars of the predator were estimated to 1.758 +/- 0.438 h(-1), 0.995 +/- 0.201 h and 0.163 +/- 0.007 h(-1), 0.038 +/- 0.002 h, respectively. For the third instar larvae of the predator, the attack coefficient (b) and handling time were 0.014 +/- 0.001 and 0.032 +/- 0.0004 h, respectively. The highest theoretical maximum predation was found for the last instar larvae of the predator followed by for second and first larval instars and estimated to 187.5, 157.89 and 36.81, respectively. Results of this study revealed that the larvae of C carnea, especially the last instar, have a good predation potential in preying on adult females of two-spotted spider mite. Therefore, by including this predator in control programs the use of pesticides against this pest will likely be reduced. However, for comprehensive estimation of the biocontrol abilities of C carnea towards acariane preys further field-based studies are needed.