printed in india 1 The searching behavior of Scolothrips longicornis (Priesner) in relation to plant surface topography The searching behavior of Scolothrips longicornis (Priesner) in relation to plant surface topography- Neda Kheradpir *1 , Mohammadreza Rezapanah 2 , Karim Kamali 1 and Yaghoub Fathipour 3 1 Dept. Entomology, Fac. of Agriculture and Natural Resources, Islamic Azad University, Science and Research Branch, P.O.Box: 14155-4933. Tehran, Iran, E-mail: n.kheradpir@gmail.com, krmkamali@yahoo.com 2 Dept. Biological Control Research, Plant Protection Research Institute of Iran, P.O.Box: 19395-1454, Tehran, Iran E-mail: rezapana@yahoo.com 3 Dept. Entomology, Fac. Agriculture, Tarbiat Modares University, P.O.Box: 14115-336. Tehran, Iran. E-mail: fathi@modares.ac.ir *E-mail: n.kheradpir@gmail.com Abstract The searching behaviour of the predaceous thrips, Scolothrips longicornis Priesner, was studied to evaluate the predator orientation toward its prey related to host plant features specially plant surface trichomes. We estimated walking speed, number of turns and orientation degree and time needed to get the first prey under laboratory condition on the undersurface of four plant species (eggplant, cucumber, tomato and sweet pepper). Eggplant with rational dense trichomes on the undersurface provided the most favorable substance for predator searching behaviour with significant difference; walking speed (6.27 ± 0.32 seconds), covered distance (20.41 ± 1.11 mm), 5.58 ± 0.76 turns and 176.66 ± 13.96 seconds. So, the predator´s searching efficiency was not similar among plant species. Thus the combined effect of plant directly on the predator walking behavior influenced the predator´s searching efficiency and it may lead to significantly different predation rate. Keywords- plant topography, Scolothrips longicornis, walking, orientation, host plant Int. J. Agric. Environ. & Biotech. Vol. 3 No. 1 March. 2010 Entomology Introduction Plant-natural enemies’ interactions include the reaction of natural enemies to chemical and physical features of host plants which would arise in natural enemies‘ preference. Although major attention has been concentrated on the host plant volatiles induced by herbivores affecting the natural enemies’ reaction toward host plants, in some cases it has been seen that plant physical structures such as color, trichomes, architecture of the plants, etc. could have major effect, too (Coll et al., 1997; Agelopoulos et al., 1999; Roda et al., 2001). A significant interaction between behaviour of natural enemies and plant architecture would be evident for the tritrophic interaction (Kareiva & Sahakian, 1990). Previous investigations of the interplay between host plant morphology and biological control agents have involved different host plants and predator species. The success of ladybird larvae Coccinella septempuntata L. in suppressing aphid population is largely related to the host plant surface structures (Bottrell et al., 1998). Trichomes are shown to be the major factors which would play opposite roles for the predator; they can alter their route toward prey and increase their handling time, or evenly prevent their oviposition as it has been seen in Anthocoris confuses Reuter (Evans, 1976). On the other hand, they can make great shelter to hide in and find more preys or provide more efficient path to catch prey (Dicke & Sabelis, 1988). Agrawal (1997) reported the effect of avocado plant trichomes on the searching time of the phytoseiids. Neoseiulus cucumeris Oudemans is affected by the Eucalyptus leaf trichomes (Beard & Walter, 2001). Some other studies showed the effect of wax layer of the leaf surface on the predators’ efficiency parameters such as predator‘s walking speed (Clark & Messina, 1998a; Clark & Messina, 1998b; Krips et al., 1999), handling time (Chang & Eigenbrode, 2004), functional response (Skirvin & Fenlon, 2001; Shiojiri et al., 2000), oviposition (Lundgren & Fenlon, 2006) and consumption rates (Kareiva & Sahakian, 1990; Grevstad & Klepetka, 1992; Heinz & Zalom, 1996; Eigenbrode et al., 1996; Agrawal et al., 2000; White & Eigenbrode, 2000; Norton et al., 2001). In a study, Clark and Messina (1998a) showed that Propylea quatuordecimpunctata L. larvae were affected by host plant species in some behavioral sequences like contacting and capturing aphids. Spider mites (Acari: Tetranychidae) are widespread pests which often cause several damage to various crops (Gerlach & Sengonca, 1985). Biological control would be a good alternative to the other control methods especially chemical control. Among the natural enemies of spider mites are predacious thrips include acarophagous species with various degree of specialization on mites. All species in the genus Scolothrips appear to be the specialized predators of spider mites (Priesner, 1950). Minute thrips of Scolothrips longicornis Priesner (Thysanoptera: