Take‐off and the ‘tarsal reflex’ in Aphis fabae

Abstract

ABSTRACT. In the transition from walking to flight in free and tethered aphids, forward progression was more or less abruptly checked and the walking pattern of leg movements gave way to a stationary, treading phase. This was followed by leg extension and wing‐spreading, kicking of the mesothoracic legs, wing‐beating and final lift‐off. Removal of the wings, but not of the middle legs, inhibited this pre‐take‐off behaviour. Jumping appeared to play no part in takeoff, nor did loss of tarsal contact stimulate flight in tethered aphids but resulted only in wing‐raising. However, restoration of tarsal contact often resulted in immediate take‐off, as well as stimulating post‐flight wing‐folding, Wing‐beating, but not wing‐raising, was apparently inhibited during walking.

Biomechanics of aerial righting in wingless nymphal stick insects

“…We hypothesize that asymmetric appendicular motions can help achieve better righting performance for more efficient reorientational rotations and post-righting manoeuvres. Rapid responses to changing airflow is physiologically feasible for volant insects, given their known capacities to incorporate motion cues via diverse sensory mechanisms, and to respond using in-flight steering with their appendages [13][14][15][16]. Similarly, a variety of wingless arthropods use appendicular and axial steering to maintain stability and to manoeuvre during gliding [17][18][19].…”

The stimuli evoking the aerial-righting-posture of falling pea aphids

“…Such inhibition is known from tethered flying insects, where removal of tarsal contact resulted in immediate activation of the flight apparatus, whereas restoring tarsal contact terminated flight (Dudley, 2000;Fraenkel, 1932;Pringle, 1938). In winged aphids (A. fabae), while removal of tarsal contact only occasionally resulted in immediate flight, tethered aphids terminated their flight when tarsal contact was reapplied (Binns, 1977). We found that in the light, the transient detachment of the tarsi from the substrate caused 60% of the aphids to move their hindlegs to the righting posture.…”

“…Do aphids assume the righting posture in response to loss of contact between their legs and the solid substrate (i.e. a tarsal reflex, sensu lato) (see Binns, 1977;Dudley, 2000;Fraenkel, 1932;Pringle, 1938), or do they sense changes in their orientation, acceleration or speed while falling through air? The distinction between the two types of cue is interesting because it reflects differences in adaptation of the sensory system for detecting a fall through air.…”

Walking and take‐off in Aphis fabae.

“…Kennedy & Booth (1963b, p. 355;1964, p. 821) concluded that the settling responses of migratory winged aphids are excited by contact with a leaf but, on an unsuitable leaf, are quickly inhibited by the light which elicits the 'antagonistic' responses of walking and take-off. Thus take-off normally follows walking (Binns, 1977a). However, for take-off to replace walking, the stimuli for take-off must be sufficiently strong and the threshold for walking must be sufficiently high.…”

“…The walking aphid is influenced kinetically by light intensity and temperature (Broadbent, 1949;Evans & Medler, 1968;Binns, 1977a), but, in addition, orients continuously to light, gravity and substrate stimuli which vary more during walking on the complex structures of a plant than do the more pervasive features of the ambient environment. Evans & Medler (1968) described Rhopulosiphum maidis orienting t o face upwards at take-off from the tip of a corn leaf, and Johnson (1958) described Aphis fubae walking up a pencil under the influence of light and gravity until they reached the tip and then took off; but these authors give n o evidence of the separate contributions of these various factors.…”