CHAPTER ONE
1.0   INTRODUCTION
        Arthropod species occur from below the soil surface to the tree canopy. However, only a small fraction are observed on a frequent basis because many are microscopic or hidden below ground or plant tissue.  Very few species are classified as pest. Whether they feed on plants or plant produce invade our homes, inflict painful bites or stings. Infect most insects and other arthropods are beneficial and serve a variety of important functions in the garden. The abundance of beneficial insects especially predators is often limited in urban landscapes because these environments typically are characterized by disturbance. Disturbance factors include use of pesticides and other chemicals, air pollution and wind-borne dust, all of which may increase mortality of beneficial arthropods. Residential landscapes often lack adequate amounts of essential resources such as food, nesting sites and shelter than enhance reproduction and survival of natural enemies. Some common strategies are employed to conserve them in residential landscapes and these strategies may help reduce insecticide use and improve plant health by enhancing natural control of arthropod pests.
        Because many arthropod pests are exotic the aim of classical biological control is to reduce pest numbers by reuniting old enemies through importation of predators from the area of insect pest origin. Lady beetles, green lace wings and spiders are familiar examples of predator arthropods inhibiting residential landscapes and gardens. In general, predators are larger than their prey, consume many prey items during their life time and feed on a broad range of species immature and/or adults may be predatory and often do not leave behind any evidence of attack.
        However, these arthropod predators often help to keep aphids, spider mites, caterpillars and other insect pests under control.