Male Depletion as a Possible Explanation for a Significant Decrease in the Number of Copulations between First and Second Mounts of the Colorado potato beetle, Leptinotarsa decemlineata
Abbott, Ashley S.
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Male and female Colorado potato beetles, Leptinotarsa decemlineata, mate multiple times with multiple partners in a polygamous mating system, where females mate repeatedly with the same male over extended periods of time. Number of copulations in first mounts, however, is significantly higher than in successive mounts. I tested whether the decrease in the number of copulations between first and second mounts was a result of male recognition of a non-virgin female, female recognition of a non-virgin male, or male sperm, nutrient, or energy depletion. I attempted to determine whether the decrease in copulations was dependent on the male or female with five treatments: 1) virgin males and virgin females; 2) virgin males and non-virgin females isolated for six days or 24 hours; 3) non-virgin males isolated for seven days or 24 hours and virgin females; 4) non-virgin males and non-virgin females; and 5) non-virgin males presented with two consecutive, but different non-virgin females. In treatments 1, 3, and 4, I found the number of copulations in second mounts to be significantly lower than the number of copulations in first mounts. Results from treatments 2, 3 and 4 showed that decrease in number of copulations between first and second mounts was not due to the previous mating status of the female. I found in treatment five that males copulated more times with the first female than with the second new female. I therefore concluded that decrease in the number of copulations between first and second mounts is due to male depletion of sperm, nutrients, water, or energy.