Many ants are well protected from predators by toxic chemicals and alarm pheromones. Wolf spiders are visual predators that attack a variety of insects, but avoid ants. Other insects can also avoid attacks by spiders if they look and smell like ants.
Gelis agilis is a wingless, ichneumon wasp that is vulnerable to attack by predators such as spiders. Gelis agilis mimics the black garden ant Lasius niger, a species that is common in its habitat. It also produces a chemical, 6-methyl-5-hepten-2-one, that is used by ant species for defense and as an alarm pheromone.
Malcicka, M. & colleagues. 2015. Multi-trait mimicry of ants by a parasitoid wasp. Nature Scientific Reports. 2015/01/27/online