The "false head" hypothesis states that due to the posterior ventral wing markings of certain butterflies which resemble a "false head," visually hunting predators, such as birds, are deceived into attacking the hind wing area rather than the true head of the butterfly. In the laboratory, six groups of artificially marked dead cabbage butterflies, Pieris rapae, were presented to Blue Jays, Cyanocitta cristata. Of the six "false head" markings, only the eyespot significantly influenced the point of attack. All of the "false head" markings, however, led to a greater proportion of attacks to the hind wing area of the butterfly. In the course of prey handling following an initial attack, each of the six "false head" markings significantly directed predator handling strikes away from the true head of captive butterflies to the anal angle of the hind wing. In a second experiment, live P. rapae with "false head" markings were mishandled and thus escaped, significantly more frequently than controls. Therefore, "false head" markings may confer a selective advantage by increasing the probability of escape, particularly during handling.

We investigated the importance of song length and singing rate in stimulating female white-throated sparrows, Zonotrichia albicollis. In November 1988 ten female and one male white-throated sparrow were captured during the fall migration. To enhance the expression of sexual receptivity, the females were implanted with 17-beta-estradiol silastic pellets. Using the visual stimulus of a non-singing male to further enhance the expression of sexual receptivity in the females, we found that females gave a greater response, in the form of copulation displays, to a five-note versus a two-note version of a typical male white-throated sparrow song. Each version was played back at four songs per minute. In May 1990 birds were captured and treated as before, except that the two-note song was played at ten songs per minute and the five-note song at four songs per minute. Therefore, each female heard twenty notes per minute. In the second experiment, the females did not show a statistical difference in response to the two-and five-note song playbacks. We interpret the results of the second experiment as indicating the song rate as well as song length is important in stimulating female whitethroated sparrows because increasing the rate of the twonote song brought the response up to the level of response we obtained to the five-note song played at the slower rate. We conclude that in white-throated sparrows, song output is important for female stimulation.

The "false head" hypothesis states that due to the posterior ventral wing markings of certain butterflies which resemble a "false head," visually hunting predators, such as birds, are deceived into attacking the hind wing area rather than the true head of the butterfly. In the laboratory, six groups of artificially marked dead cabbage butterflies, Pieris rapae, were presented to Blue Jays, Cyanocitta cristata. Of the six "false head" markings, only the eyespot significantly influenced the point of attack. All of the "false head" markings, however, led to a greater proportion of attacks to the hind wing area of the butterfly. In the course of prey handling following an initial attack, each of the six "false head" markings significantly directed predator handling strikes away from the true head of captive butterflies to the anal angle of the hind wing. In a second experiment, live P. rapae with "false head" markings were mishandled and thus escaped, significantly more frequently than controls. Therefore, "false head" markings may confer a selective advantage by increasing the probability of escape, particularly during handling.

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