Why don鈥檛 insects 鈥� particularly flies, wasps and bees 鈥� fly in straight lines like most birds do? Their flight patterns seem chaotic and often circular in motion. Surely it is inefficient for them to fly in such a random way?
鈥� Birds seldom fly in straight lines, in fact, and any self-respecting ornithologist can identify many species by flight pattern alone. That said, birds tend to fly fairly directly to a target in sight, and more complex journeys tend to follow efficient paths based on learned topography.
Insect flight is much more varied. Their flight patterns partly compensate for their typically poor eyesight, by allowing them to gather more visuospatial information.
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When insects do have a path in mind, many fly directly enough, as anyone who has been stung can attest. In threat display, a bee buzzes wildly, but a true attack is like a projectile from a pea-shooter. In searching, scent-following, mating assembly, territorial patrol and so on, insect flight patterns are not straight, but they do resemble corresponding vertebrate behaviour.
Differences between, say, insects鈥� apparently chaotic swarms and skeins of large birds do not reflect their psychology but rather their size difference, which affects wing motions and the benefits of flying in fixed formation. Flocks of small birds such as starlings or queleas can look very locust-like.
Jon Richfield, Somerset West, South Africa
鈥� Judging insect flight depends on the scale you choose. If you watch a metre of flight and you see the insect travelling in a straight line you might conclude it does this all the time. But if you observe a kilometre of flying the picture is quite different.
When insects are searching, their flight is an intermittent combination of long and short-distance steps where each step differs from the previous one by a small angle. Small steps are the most frequent, while very long steps are rare. This is an optimal searching strategy known as 鈥�L茅vy flight鈥�. It seems chaotic but it is not, the angles and the distance follow well-defined statistical distributions. In the case of bees, they fly in amazingly straight lines for kilometres once they know where a food source is. When they aren鈥檛 flying 鈥渞andomly鈥�, a straight line is the best way to go.
鈥淚nsect flight may seem chaotic or random but it is not, it follows defined statistical distributions鈥�
For two studies on such behaviour, visit and .
Octavio Miramontes, Mexico City, Mexico
鈥� Insects do not have vision as sharp as that of mammals or birds. The insect compound eye is more attuned to movement and so it cannot precisely position distant objects. As a result, insects tend to take a rather wobbly flight path to navigate to a particular object.
Additionally, many insects navigate using scent. Take the case of a parasitic wasp that is seeking a caterpillar in which to deposit its eggs. In order to locate the caterpillar, the wasp needs to balance the odour signals received by its two antennae. This necessitates a rather wobbly flight path to 鈥渓ock on鈥� to the source of the scent. When an insect is close to the object it is seeking this wobble starts to reduce and eventually the insect becomes capable of very precise, rapid actions, such as those of a dragonfly catching a prey insect when both are in mid-flight.
The 鈥渞andom鈥� movement is a simple product of insect sensory systems. Humans rely on vision to navigate the world 鈥� just try locating an open bottle of perfume in a room with your eyes closed.
鈥淗umans rely on vision rather than smell. Try locating a bottle of perfume with your eyes shut鈥�
Peter Scott, School of Life Sciences, University of Sussex, Brighton, UK
If readers are interested in how humans can be taught to follow scent trails in the way that dogs and other animals can, then the following story will enlighten them: 鈥�Unleash your inner bloodhound 鈥� start sniffing鈥� 鈥� Ed
鈥� I suspect evolution wasted no time in eliminating those insects which fell easy prey to bats, birds, frogs and the like because of their use of efficient and direct 鈥� but predictable 鈥� flight patterns. Presumably those insects with variable patterns are those that survived until today.
Peter Tredgett, Llanbedrog, Gwynedd, UK