Although frequently observed in natural habitats across Israel, the true nature of the "strange growths" (galls) that appear on various plants is not always clear. Insect-induced plant galls are actually the most intimate way in which animals feed on plants. This book reveals to naturalists and scientists one of the most impressive and conspicuous groups among gall-forming insects: aphids that form galls on wild pistachio (Pistacia). The gall serves as an incubator for the aphids, providing them with a rich food supply and shelter from natural enemies and abiotic factors. Several aphid generations develop in galls from spring to fall. During these months, the gall functions as a dynamic and complex multitrophic ecological (mini) system, including pathogens, competitors, parasites, and predators. The first part of the book describes the multi-disciplinary information on the biology and ecology of the aphids and gall system from molecular, anatomical, physiological, biochemical, behavioral, biogeographic, and evolutionary points of view. The second part of the book is in fact an informative and photographic guide to all the aphid-induced galls on wild pistachios in Israel.