The fixation point
Information about the fixation point may be obtained from tracks with a rotating female. This will be explained by a simplified animation. In the animation a female is rotating 90 degrees. In the animation the position of the female is given as seen by the male from above. The male is controlling its position right above a point on the thorax of the female, the red point in the animation. The x-axis is vertical. In the diagram time is indicated along the horizontal axis. The distance of the Male head to the Female Scutellum and the Female Head is graphed along the verical axis.
The animation does approximately fit the results for a real Male and Female as given in Fig. 1.  In Fig 1 the female is rotating between time 1.2 and 2.2 (s). The horizontal distance from the male head (face) is given for the female scutellum and the female head (ocelli). In both cases the distance from the male head is changing with time, allthough in different directions. For the fixation point the distance to the male head does not depend on the rotation of the female. The bold lines in Fig 1a and Fig 1b have been calculated from the mean position before and after the rotation of the female. In the case of Fig 1 the fixation point is situated between the female head and scutellum.


Figure 1 :  Information about the fixation point of the male in track 090704_1504A_B10 (see Materials and Methods).  The distance given is the distance, in the horizontal direction, with the head of the male as the centre of co√∂rdinates.  Bold lines in a) and b) are calculated from the mean of the first part and the mean of the last part of the signal.

The estimated fixation points for some tracks are given in Fig 2. The fixation points are more or less evenly distributed with most points on the thorax. Fig 2 is from different films and probably different individuals, so there may be individual preferences. The fixation points are calculated using a least squares algorithm. The algorithm may be found here.


Figure 2: The fixation points.

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