There are three spiders and an ant on the edges of a wireframe regular tetrahedron. The spiders all move at the same speed, which is faster than that of the ant. Though the ant can always see the spiders, the ant is invisible. A spider can only detect the ant by being on top of it, in which case the ant is immediately eaten. Show how the spiders can catch the ant.
This is rather similar to an earlier puzzle I posted. The differences are that the cube is now a tetrahedron, the spider's speed increased from $\frac13$(fly's speed) to (fly's speed)$+\varepsilon$, and the fly is now invisible. The first two changes greatly help the spider, but this is still a harder puzzle.