Insect Locomotion

Terrestrial Locomotion

Having 6 legs, insects move on alternating sets of tripods. The three blackened legs are those in direct contact with the ground; the yellow legs are being lifted and moved forward.

General principals of insect walking

1.  No leg is raised until the leg behind it is in supporting position.
2. Within a segment the legs alternate while moving. One leg moves forward while the leg on the opposite side remains on the ground.

A centipede was happy, quite,
Until a toad in fun
Said, "Pray, which leg moves after which?"
Which raised her doubts to such a pitch,
She fell exhausted in the ditch,
Not knowing how to run.

Soft bodied caterpillars are not able to move in this fashion which requires a rigid frame. They move by peristaltic movement. They creep forward by pulling the rear prolegs forward, grab with the prolegs and then push the front of the body forward.

Aquatic Locomotion

How aquatic insects move depends on their ability of the insect to breathe. Some have gills or siphon tubes which allow them to stay underwater permanently. Others carry a bubble of air for extended periods of underwater movement. Others stay on the surface or periodically return to it to renew their air supply.

Two General Adaptations:

1. To move upon or at the top of the water
2. To swim under water

Surface Walkers because of their small size are able to walk on the water surface tension. May use hairs to increase their surface area or wax to make themselves more water repellent.

Aerial Locomotion

The only invertebrates and the first animal group able to fly.

The first flying insects moved their wings by direct muscle attachment. Direct muscle attachment is the primitive state.

Direct muscle - ex. human arm. Direct muscle is attached to arm bone and pulls

directly on the bone.

Direct muscle attachment, the primitive state for insect wings

Indirect Flight Muscles of insect wing

Indirect muscles are more efficient and capable of a higher wing beat frequency.

Insect Wing beat frequency and flight speed

Insect	beats/second	flight speed km/hour
dragonfly	20-28	25
beetles	46-90	5
butterflies	9-12	9
hawk moth	70-85	18
mosquito	300-550	32
horsefly	100	22
honey bee	200	22
wasp	110	9

Movement - body lengths per second

• human - 5
• Volkswagen 'beetle' - 5
• jet fighter plane - 100
• fly - 250 to 300

Wing Structure

Except for a few primitive insect groups, all insects are winged or are secondarily wingless (wings lost from groups whose ancestors were winged).

Insect veins are apparent on most insect wings. Veins serve two purposes.

1. To inflate the wings of insects emerging from pupae
2. To provide rigidity and structural support to the wing

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Last updated Jan. 18, 1999
Gary Brewer