This book describes the pattern of an aphid parasitoid community in field and horticultural crops in Rawalpindi division. Aphids are the serious pest of field and horticultural crops in Pakistan. They not only lower the yield of crops but also serve as the vector of plant viral diseases. In Pakistan, aphids have mostly been restricted by insecticidal applications. Nevertheless, due to undesirable effects of insecticides, total dependence on them can not be made. The parasitoid represents an important element in the aphid environment. During the study ten aphid species and eleven parasitoid species were identified. The mean density of aphid and parasitoid were 63.07 and 8.64 per m2 respectively. It was found that the populations of primary parasitoid of aphids were directly proportional to the population of aphids. Eleven quantitative aphid parasitoid food webs were constructed describing the trophic relationships between the community of aphids and primary parasitoids. All aphid parasitoids food web links were expressed in the same m2 unit.