In experiments involving male crickets, they gauged differences in male singing in part by capturing males, placing them in containers in the field, then recording them during spring and fall. They also surveyed free singing males in a pasture during the two seasons.
In North Florida, the parasitic flies are present only in fall, never in spring. The researchers findings seemed to agree with this schedule. More of the males sang in the spring than in fall, with 75 percent of the captured males, for example, singing in spring and 43 percent in fall.
To test how female crickets respond to the flies, the scientists captured and placed spring and fall females in cages, then played recordings of male songs and observed their reactions. Paralleling the result with the males, more of the spring females approached the speaker quickly and more closely than the fall females.
"The spring females are extremely eager. The minute they hear a male singing, they race over to the speaker," Brockmann said. "The fall females are much more hesitant. They take longer and seem reluctant to approach the speaker."
Brockmann said although scientists have examined similar phenomena in other species such as guppies, it is rare to observe obvious female courtship behaviors. Female crickets, by contrast, actually mount the males, so it is easy to know what they are choosing. Also, she said, the complete absence of parasitic flies in spring allows the researchers to examine the role of flies as a selective pressure on male singing and female mate choice behavior.
That said, not all of the findings were clear-cut. Although fewer males sing in the fall, for example, the ones that sing do so far longer, placing themselves at even greater jeopardy of being parasitized by the flies. Brockmann said this may reflect the presence of many more females in the fall, enabling
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Contact: Jane Brockmann
hjb54@ufl.edu
352-392-1297
University of Florida
13-Dec-2006