bark of pawpaws contain natural insecticides known as acetogenins. Pawpaw leaves and twigs are seldom consumed by rabbits, deer, or goats, or by many insects. However, mules have been seen eating pawpaw leaves in Maryland. Larvae of the zebra swallowtail (Protographium marcellus), a butterfly, feed exclusively on young leaves of A. triloba and various other pawpaw (Asimina) species, but never occur in great numbers on the plants. Chemicals in the pawpaw leaves confer protection from predation throughout the butterflies' lives, as trace amounts of acetogenins remain present, making them unpalatable to birds and other predators. Other insects which have evolved the ability to consume pawpaws include Talponia plummeriana, the pawpaw peduncle borer, whose larvae can be found in flowers, and Omphalocera munroei, the asimina webworm, whose larvae mostly feed upon leaves. Pollination The floral scent of Asimina triloba has been described as "yeasty," which is one of several features that signify a "beetle pollination syndrome." Other floral features of pawpaw indicative of beetle pollination include petals that curve over the downward-pointing flower center, along with food-rich fleshy bases of the inner whorl of petals. A "pollination chamber" is thereby created at a depth that only small beetles can access during the initial female-receptive stage of floral bloom. As with other well-studied species of Annonaceae, the delay in the shift from female to male floral stage offers beetles a secure, and possibly thermogenic, residence in which not only to feed but also to mate. Receptive stigmas at their arrival, followed by pollen-shedding stamens during pollinator departure is regarded as an early form of mutualism (biology) evolved between plants and insects that is still dominant in the most ancient lineages of flowering plants, including the Magnoliids (of which Annonaceae is the most species-rich taxonomic family). Beetles are the dominant form of pollinator ascribed for genera and species within Family Annonaceae. However, two species of genus Asimina (Asimina triloba and Asimina parviflora) bear a floral character that has given rise to an alternative hypothesis that carrion or dung flies are their effective pollinators. That floral characteristic is the dark maroon color of the petals. Hence, while no scholarly papers have documented carrion or dung flies as effective pollinators in field observations, the strength of this hypothesis has led to placement of carrion during the bloom time in pawpaw orchards by some horticultural growers. Professional papers on genus Asimina and its species have warned