TAKE-OFF TRADE OFF

When a fly launches itself from a surface, it has a choice of techniques;it can simply fling itself into the air when startled, or it can coordinate its first wing beat with a jump for a stable voluntary departure. The two approaches are governed by different neural pathways linking the insect's brain to its wings and legs. However, the escape pathway, coordinated by the giant fibre interneurons, is essentially a reflex and much simpler than the voluntary take-off pathway. Gwyneth Card and Michael Dickinson wondered why flies have developed two take-off pathways when one would seem sufficient(p. 341). Analysing high speed film of both techniques, the team realised that beating the wings during a voluntary take off results in a slow but controlled departure. However, when the flies launched themselves by leaping to escape, they only unfurled their wings several wing beats later, resulting in a fast but relatively chaotic take off. Card and Dickinson suspect that the flies trade off stability for speed during an escape. And having scrutinized the flies'preparations for take off, the team propose four possible independent take-off pathways, suggesting that flies could tailor their escape to a threat's significance.