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Mating Walnut Flies: Mating scenarios -- no graphics

This page is intended to be read aloud by a screen reader such as JAWS. It is long (nearly 2000 words).

Narrative for walnut fly mating scenarios.

Female-biased sex ratio
Long copulations

In this scenario there is a sex ratio of 2 females to every male. This is a female-biased sex ratio. The focal male (that is, the fly whose behavior you will observe) in this scenario is a "long-copulation" male. The longer a male copulates, the more eggs he fertilizes per female. However, the gain in eggs fertilized levels off over time - in other words, it is not linear. With each additional unit of time, fewer and fewer additional eggs are fertilized.

At the beginning of this scenario, you are observing a group of male and female walnut flies in an arena. There are eight females and four males. You will follow the activities of one male walnut fly - the "focal male." As each unit of time passes, you will receive information on the activities of the focal male, how many females he has mated with, and how many eggs he has fertilized. At the end of the scenario, which runs for 20 units of time, you will learn how many females he mated with, how many total eggs were fertilized by the focal male, and his overall fertilization rate, expressed in eggs fertilized per unit time. Be sure to record the final numbers, as you will be asked about them later on.

You are now at time unit 1. The focal male is not mating with anyone. Of the available females, two are mating with other males.

Time 2
The focal male has begun mating with one of the free females. So far he has fertilized 5 of her eggs.

Time 3
The focal male continues mating with the same female. Now he has fertilized 8 eggs, a gain of 3 eggs.

Time 4
The focal male continues mating with the same female. Now he has fertilized 11 eggs, a gain of 3 eggs.

Time 5
The focal male continues mating with the same female. Now he has fertilized a total of 12 eggs, a gain of 1 egg.

Time 6
The focal male continues mating with the same female. Now he has fertilized a total of 13 eggs, a gain of 1 egg.

Time 7
The focal male has stopped mating with the first female. There are plenty of other females free.

Time 8
The focal male begins mating with a second female. So far he has fertilized 5 of her eggs, for a total of 18 eggs fertilized.

Time 9
The focal male continues mating with the second female. He has fertilized an additional 3 of her eggs, for a total of 21 eggs.

Time 10
The focal male continues mating with the second female. He fertilized an additional 3 eggs, for a total of 24.

Time 11
The focal male is still mating with female two. His fertilization total is 25 eggs.

Time 12
Still mating; he's now up to 26 eggs.

Time 13
The focal male has stopped mating with the second female. There are still plenty of other females free.

Time 14
The focal male begins mating with female number three. He fertilizes 5 of her eggs for a total of 31 eggs.

Time 15
Still mating. Up to 34 eggs now.

Time 16
Still mating. Up to 37 eggs now.

Time 17
Still mating. Up to 38 eggs now.

Time 18
Still mating. Up to 39 eggs now.

Time 19
The focal male has stopped mating with the third female. He fertilized 13 of her eggs, for a total of 39 eggs. Still plenty of free females.

Time 20
This is the last Time in this scenario. The focal male has begun mating with his fourth female, and fertilized 5 of her eggs so far, for a total of 44 eggs. His egg fertilization rate, which is the number of eggs he fertilized (44) divided by the units of time (20), is 2.20 eggs per time. To recap: he mated with four females, fertilizing a total of 44 eggs, for a rate of 2.20 eggs per time. End of scenario.

Second Scenario
Female-biased sex ratio
Short copulations

In this scenario the sex ratio is 2 females to every male. The focal male is one that copulates for a short period of time. Again, you are observing a group of male and female walnut flies in an arena. There are eight females and four males. You are now on Time one. The focal male is not mating with anyone. Of the available females, two are mating with other males.

Time 2
The focal male has begun mating with one of the free females. So far he has fertilized 5 of her eggs.

Time 3
The focal male continues mating with the same female. Now he has fertilized 8 eggs, a gain of 3 eggs.

Time 4
The focal male has stopped mating with the first female. There are plenty of other females free.

Time 5
The focal male continues mating with the second female. He fertilizes 5 of her eggs for a total of 13 eggs.

Time 6
The focal male continues mating with the second female. Now he has fertilized a total of 16 eggs, a gain of one egg.

Time 7
The focal male has stopped mating with the second female. There are plenty of other females free.

Time 8
The focal male begins mating with a third female. He fertilizes 5 of her eggs, for a total of 21 eggs fertilized.

Time 9
The focal male continues mating with the third female. He has fertilized an additional 3 of her eggs, for a total of 24 eggs.

Time 10
The focal has stopped mating with female number three. There are still plenty of free females.

Time 11
The focal male begins mating with female four. He fertilizes 5 of her eggs, for a total of 29 eggs.

Time 12
Still mating with the fourth female. Total eggs fertilized now 32.

Time 13
The focal male has stopped mating with the fourth female. There are still plenty of other females free.

Time 14
The focal male begins mating with female number five. He fertilizes 5 of her eggs for a total of 37 eggs.

Time 15
Still mating. Up to 40 eggs now.

Time 16
The focal male stops mating with the fifth female. Still plenty of free females.

Time 17
The focal male begins mating with the sixth female. Eggs fertilized now 45.

Time 18
Still mating. Up to 48 eggs now.

Time 19
The focal male has stopped mating with the sixth female. Still plenty of free females.

Time 20
This is the last Time in this scenario. The focal male has begun mating with his seventh female, and fertilized 5 of her eggs so far, for a total of 53 eggs. His egg fertilization rate, which is the number of eggs he fertilized (53) divided by the units of time (20), is 2.67 eggs per time. To recap: he mated with seven females, fertilizing a total of 53 eggs, for a rate of 2.67 eggs per time. End of scenario.

Third Scenario
Male-biased sex ratio
Long copulations

Now the sex ratio is 1 females to every 2 males. This is called a male-biased sex ratio. The focal male is one that copulates for a long period of time. At the beginning of this scenario, you are observing a group of male and female walnut flies in an arena. There are four females and eight males. You are now on Time one. The focal male is not mating with anyone. Of the available females, all but one are mating with other males.

Time 2
The focal male has begun mating with the one free female. So far he has fertilized 5 of her eggs.

Time 3
Still mating with first female, the focal male has now fertilized 8 eggs.

Time 4
Still mating with the first female, the focal male has now fertilized 11 eggs.

Time 5
Still mating. Egg count now 12.

Time 6
Still mating. Egg count now 13.

Time 7
The focal male has stopped mating with the first female. At this time, there are no other females free.

Time 8
Still searching for a free female, but none are to be found.

Time 9
Still searching.

Time 10
One of the other males has stopped mating with a female, who is now free. The focal male approaches her.

Time 11
The focal male begins mating with his second female. Eggs fertilized rises from 13 to 18.

Time 12
Still mating; egg count now 21.

Time 13
Still mating; egg count now 24.

Time 14
Still mating; egg count now 25.

Time 15
Still mating, egg count now 26.

Time 16
The focal male stops mating with the second female. There are no other females free (the first female he mated with is currently paired with another male).

Time 17
Still searching.

Time 18
One of the females becomes free.

Time 19
The focal male approaches the free female.

Time 20
End of scenario. The focal male begins mating with his third female, and fertilizes 5 of her eggs, for a total of 31 eggs. His egg fertilization rate, which is the number of eggs he fertilized (31) divided by the units of time (20), is 1.55 eggs per time. To recap: he mated with 3 females, fertilizing a total of 31 eggs, for a rate of 1.55 eggs per time. End of scenario.

Fourth Scenario
Male-biased sex ratio
Short copulations

The sex ratio is 1 females to every 2 males. The male is one that copulates for a short period of time. At the beginning of this scenario, you are observing a group of male and female walnut flies in an arena. There are four females and eight males. You are now on Time one. The focal male is not mating with anyone. Of the available females, all but one are mating with other males.

Time 2
The focal male has begun mating with the one free female. So far he has fertilized 5 of her eggs.

Time 3
Still mating with first female, the focal male has fertilized 8 eggs.

Time 4
The focal male stops mating with the first female, but there are no other females free.

Time 5
Still searching, but unsuccessful.

Time 6
Still searching. A female becomes free.

Time 7
The focal male approaches the free female.

Time 8
The focal male begins mating with his second female. Egg count up to 13.

Time 9
Still mating with female number two. Egg count 16.

Time 10
The focal male stops mating with the second female. There are no other females free.

Time 11
Still searching, but unsuccessful.

Time 12
Still searching. A female becomes free.

Time 13
The focal male approaches the free female.

Time 14
The focal male begins mating with his third female. Egg count 21.

Time 15
Still mating, egg count up to 24.

Time 16
The focal male stops mating with the third female. There are no other females free.

Time 17
Still searching, but unsuccessful.

Time 18
Still searching. A female becomes free.

Time 19
The focal male approaches the free female.

Time 20
End of scenario. The focal male begins mating with his fourth female, and fertilizes 5 of her eggs, for a total of 29 eggs. His egg fertilization rate, which is the number of eggs he fertilized (29) divided by the units of time (20), is 1.45 eggs per time. To recap: he mated with 4 females, fertilizing a total of 31 eggs, for a rate of 1.45 eggs per time. End of scenario.

You have now observed all four scenarios.