BATESIAN MIMICRY: FIELD DEMONSTRATION OF THE SURVIVAL VALUE OF PIPEVINE SWALLOWTAIL AND MONARCH COLOR PATTERNS

Batesian mimicry is a means of avoiding predation and results from the advergence (Brower and Brower, 1972) in shape, pattern, color or behavior of an edible mimic to resemble a less palatable and more or less distantly related model. The efficacy of Batesian mimicry has been demonstrated with caged predators, but its selective value in nature remains to be definitively demonstrated. L. P. Brower and associates attempted such a demonstration on Trinidad, using a novel release and recapture technique which may have partially demonstrated that Batesian mimicry is effective, but they eventually concluded that their results were inconclusive (Brower et al., 1964; Brower et al., 1967; Cook et al., 1969; Waldbauer and Sternburg, 1976). Our field studies have shown that the color pattern of an insect affects the rate of predation on it (Sternburg et al., 1977). These studies, conducted in a Central Illinois woodland, entailed painting the black, diurnal males of a saturniid moth, Callosamia promethea Drury, to resemble the yellow tiger swallowtail (Papilio glaucus L.), a palatable butterfly, and similarly painting equal numbers of male promethea with black paint which did not significantly alter their appearance. The latter moths resembled the local, unpalatable swallowtail Battus philenor (L.) (J. Brower, 1958b). We released painted moths on twelve occasions from May through August, 1975, in the center of a one mile diameter circle of traps baited with pheromone-releasing, virgin, female promethea. We recaptured a high percentage of the painted moths and assumed that differential recapture indicated differential predation. Statistical analyses of our data revealed three significant trends: 1) we recaptured fewer yellow than black-painted moths; 2) the black-painted moths tended to survive longer in the field; and 3) the yellow-painted moths sustained much more wing damage than did the black. We attribute much of this damage to bird attacks. Based on these data we proposed that Callosamia promethea males are either Batesian mimics of the toxic aristolochiafeeding swallowtail Battus philenor and are thus protected from predators (Edwards, 1884; Poulton, 1909; Waldbauer and Sternburg, 1976), or that the yellowpainted moths were simply more conspicuous to predators and consequently were attacked more often. Unfortunately, our experimental design did not permit us to distinguish between these two possibilities. Platt and Brower (1968) stated that the yellow and black pattern of Papilio glaucus (we would also include P. cresphontes Cramer), is disruptive, i.e., it breaks up the outline of the insect making it difficult to see. We agree with this observation and are convinced by our experiences in the field that yellow forms of P. glaucus, P. cresphontes and our yellow-painted males are less conspicuous in either woodland or open fields than are the various black swallowtails and the unaltered or blackpainted promethea males. Nevertheless, to eliminate the variable of the relative conspicuousness of the color patterns, we modified the experimental design used in the previous study. Three groups of male promethea were painted with black, yellow, or orange to resemble respectively, B. philenor, P. glaucus, or Danaus plexippus (L.) (the monarch). The latter two are almost equally bright and conspicuous to the human eye, but one resembles an edible butterfly while the