On Country

Angle of a Projectile from an antlion’s pit

Reference:

http://www.antlionpit.com/antlions.html

Follow the prompts to the antlion behaviour and life cycle.

• The antlion (the larva of the Lace-wing fly) digs a pit in loose dry sandy soil with a spiral action, throwing the sand up and outwards with its head. It appears to be selecting the size of the sand grains, as it throws the larger ones out, retaining the finer ones.

• In addition, it engineers the angle of the side of the pit to 30o. This ensures the fine particles (which will have less momentum) stay on sloping walls, while larger particles (which will have greater momentum) tend to fall to the centre, the fate of a future prey.

• It is thus the size of the sand grain and the angle of the sides of the pit that ensure an ant will be carried into the waiting jaws, just visible at the bottom of the pit.

• The antlion clamps them around the prey, injects a toxin and proceeds to suck the soft inner parts of the ant.

• When finished, it tosses the exoskeleton of the ant out of the pit – at an angle of 45o.

• This is the angle (well known to javelin throwers), that will maximise the distance travelled of a thrown (or projected) object.