Alightment of Apple Maggot Flies on Fruit Mimics in Relation to Contrast Against Background

Abstract

I evaluated an hypothesis, developed from earlier studies, that apple maggot flies, Rhagoletis pomonella (Walsh), within a tree should be better able to find fruit of any color when looking outward or upward rather than inward or downward. Artificial fruit mimics were created by covering all or half of 6-cm-diam rubber spheres with red or green artist pigments whose reflectance spectra closely matched those of natural red or green fruit. Numbers of flies alighting on such mimics placed in apple trees revealed that response was (a) greater to red than green pigment, irrespective of pattern of pigment distribution, (b) greater to bi-colored mimics whose red half faced downward as opposed to upward, and (c) no different to bi-colored mimics whose red half faced inward compared with outward. Possible explanations for partial but not full support of the hypothesis are discussed.