Defensive ant, aphid and caterpillar mimicry in plants?

Abstract

Here we describe three apparently novel types of visual insect mimicry in plants. In the first type, plants of Xanthium trumarium L. have dark spots and flecks that resemble ants (Formicidae) in size and shape in the epidermis of stems, branches and petioles, and plants of Arisarum vulgare Targ.-Tozz. have them on petioles and inflorescence stems. In the second type, the dark anthers of Paspalum paspaloides (Michaux) Scribner (= P. distichum) are the size, shape and colour of aphids (Homoptera; Aphidoidea) and they sway in the wind like swivelling aphids. Similarly, the stems of Alcea setosa (Boiss.) Alef. are covered with dark flecks that look like aphids. Finally, immature pods of three wild annual legumes (Lathyrus ochrus (L.) DC.; Pisum fulvum Sm.; Vicia peregrina L.) have conspicuous reddish spots, arranged along the pods, that appears to mimic lepidopteran caterpillars. In one of the species (V. peregrina) two different mimicking morphs were found. We propose that these morphological traits may serve as herbivore repellent cues and are part of the defence system of the plants. © 2002 The Linnean Society of London.