Showing papers by "Hermann Wagner published in 1986"

Flight performance and visual control of flight of the free-flying housefly (Musca domestica L.) II. Pursuit of targets

Abstract: The pursuit behaviour of houseflies has been analysed by the evaluation of movie films. On the floor, males, but not females, turn towards passing targets. Males as well as females pursue targets in the air. Male chasing seems to be functionally different from female tracking. Males attack targets in the air from below. They sometimes retract from the target fly after an approach. Thus, a chase may be divided into attacks, periods of pursuit and retreats. Males catch females, but not other males. The pursuer is therefore able to discriminate between the sexes. Close approach or contact with the target fly seems to be necessary to obtain the information. During pursuit both sexes increase the rate of turning. The male but not the female target fly performs evasive translatory reactions to the attacks (figure 4). Females do not catch other flies. They often react with a single turn in the direction of a passing object. They seldom follow the target, which is then normally positioned below the tracking fly. The rotations about the vertical and transverse axis (yaw and pitch) are visually controlled in both sexes. The horizontal and vertical error angle, as well as the horizontal and vertical retinal target velocity, influence the turning behaviour. At least in males, further, hitherto unknown, cues seem to be additionally involved in the control of the rotatory movements. The male control systems operate more precisely than those of the females. Rotations are characterized by steplike changes in angular orientation (`turns') at high angular velocity. Smooth rotations at angular velocities less than about 200 deg s^(-1) seem not to play any role either in males or in females. `Sideways' tracking, most probably mediated by rolling about the long axis, occurred in a single sequence only. A correlation between the translation velocity and the distance between pursuer and target is observed in the pursuit sequences of both sexes. This correlation is interpreted as a by-product of the organization of the flight motor. Therefore, neither males nor females control the translation velocity by the distance to the target. The discussion concentrates on the problems in characterizing the control systems and a comparison with data from optical and electrophysiological measurements. The behavioural differences between hoverflies and houseflies are attributed to the different flight motors.

Flight Performance and Visual Control of Flight of the Free-Flying Housefly (Musca Domestica L.) I. Organization of the Flight Motor

Abstract: Free-flying houseflies have been filmed simultaneously from two sides. The orientation of the flies' body axes-in three-dimensional space can be seen on the films. A method is presented for the reconstruction of the flies' movements in a fly-centred coordinate system, relative to an external coordinate system and relative to the airstream. The flies are regarded as three-dimensionally rigid bodies. They move with respect to the six degrees of freedom they thus possess. The analysis of the organization of the flight motor from the kinematic data leads to the following conclusions: the sideways movements can, at least qualitatively, be explained by taking into account the sideways forces resulting from rolling the body about the long axis and the influence of inertia. Thus, the force vector generated by the flight motor is most probably located in the fly's midsagittal plane. The direction of this vector can be varied by the fly in a restricted range only. In contrast, the direction of the torque vector can be freely adjusted by the fly. No coupling between the motor force and the torques is indicated. Changes of flight direction may be explained by changes in the orientation of the body axes: straight flight at an angle of sideslip differing from zero is due to rolling. Sideways motion during the banked turns as well as the decrease of translation velocity observed in curves are a consequence of the inertial forces and rolling. The results are discussed with reference to studies about the aerodynamic performance of insects and the constraints for aerial pursuit.

Flight Performance and Visual Control of Flight of the Free-Flying Housefly (Musca Domestica L.) III. Interactions Between Angular Movement Induced by Wide- and Smallfield Stimuli

Abstract: The flights of free-flying houseflies are analysed in different behavioural and environmental situations. The angular movements about the vertical body axis are characterized by a cascade of steplike changes of long axis orientation (`turns'). Most of these turns are separated by periods of little or no rotation. Turns about the vertical axis are short (under 120 ms). They are performed at angular velocities of up to about 4000 deg s^(-1). These characteristics are found (i) when a single fly cruises in a stationary environment; (ii) if the visual input is eliminated; (iii) if a textured surround (optomotor stimulus) is moved around the fly; (iv) during visually guided pursuit of small targets in stationary as well as in moving environments. Optomotor stimulation increases the number of turns in the direction of pattern motion relative to those against it. This leads to a correlation between the average angular velocity of the fly and the stimulus velocity. However, optomotor stimulation does not interfere with chasing and tracking. A model is proposed that qualitatively accounts for the observed behaviour in free flight of houseflies.