Myrmarachne assimilis is the only Myrmarachne species that mimics the aggressive weaver ant, with which it lives in close contact. Not only do they look alike and walk alike, it is also thought that Assimilis has developed a way to copy the chemical signatures the weavers use to recognize each other.
Amazingly, the baby spiders, when they are too minute to convincingly copy the much bigger ant species that the adult copies, use other smaller ant species as a model.
Myrmarachne melanotarsa, also called the dark-footed ant-spider, is an African jumping spider found around in Africa. This Myrmarachne mimics ants, like many other Myrmarachne, of the Crematogaster genus. However, these guys are unusual in that they exhibit social behavior, forming large communities. Hundreds of these spiders, of both sexes and of all ages, can be found in such communal nests, but most nests have between 10 and 50 spiders. It is theorized (and has been witnessed) that when Melanotarsa travels in larger groups (like ants do) they are much less likely to be attacked by specialist spiders - who actually prey on ant-mimics.
For many salticids (jumping spiders), ants can be very dangerous... but salticid eyesight seems to be up to the challenge. Some experiments have demonstrated that many species of ordinary salticids (species that are neither ant-like nor ant-eating) readily identify ants by sight and then avoid their proximity.
Ant-like and ant-eating salticids NEED to get close to ants, however, and they apparently have abilities to survive these close encounters better than other salticids. It has been thought that accurate mimics of a particular model species survive better ... but a brand new study might suggest that imperfect mimics possibly do better than their perfect couterparts.
Synemosyna formica is thought to mimic Pseudomyrmex gracilis, a nasty little a-hole that can both jump and sting.
This ant-like salticid is found from the northeastern United States southwest to Mexico. These could not look more like the super-aggressive harvester ants of the region. Specifically, note the markings on the spider's upper thorax that looks like big, bambi ant eyes.
The house I grew up in had regular infestations of these ridiculously mean little biting assholes, and I am pretty sure I would have preferred living with the spider version.
Aphanlochilus is a sly predator. Unlike many of the spiders and insects on this list, this guy looks and acts like the ants he eats. He can approach the colony without causing alarm because of his looks and his demeanor... but will strike when he gets close enough. This amazing picture (which I'm totally crediting to Alex Wild who takes stunning macros of insects & arachnids) shows Aphanlochilus rogersi holding one of its victims snatched from a column of foraging ants.
This particular spider is so specialized as a predator of these specific ants that they refuse to eat other types of insects. They not only blend in with ants by looking like them, they also hold their catches in a way that makes it look like they are just another member of the colony holding a deceased companion.
The Kerengga Ant-like Jumper mimics ant-like behaviour by the style of locomotion and by the way they wave their front legs like antennae to mimic the ants. These jumping-spiders jump only when their safety is threatened. Unlike the pissy, aggressive ants they mimic, they don't bite people.
This is an insect, a Treehopper, our first non spider on this list. The 'ant' that's apparently riding on the back of the treehopper is actually an extension of its headshield. The green coloration of the rest of its body blends in with its leafy background, so on first glance you only see the black 'ant'. The mimic is seated in reverse: if you look carefully at the 'abdomen' of the 'ant', you'll see the green eye of the treehopper staring right back at you. This makes sense because in their defensive posture, ants move backwards.
This function is simple halloween maskery. "I'm an ant! I taste really bad! And I have a zillion pals nearby to come kill you if you touch me!" ..."Ahem, got that?"
Army ants (also known as Driver Ants) are the carnivorous marching columns of death that obliterate anything that cannot flee from their path. These soldiers almost create their own ecosystem, because they have groupies that live with and/or follow their trail. As dangerous as it is for some insects to be in the path of the ant army,the Staphylinid Beetle SHARES the nest of these killers.
The Staphylinids can look, smell, act and even sound like their ant host species so that the ants don't think they're intruders. Some species of adult staphylinid beetles have evolved to look like ants, but they are also capable of mimicking the chemical signature of their host. The beetle has a glandular secretion that actually attracts the ant. The ant will 'adopt' the beetle and obligingly carry it right into the nest. The beetles then have access to the ants' food. On rare occasions when there is no food, the beetles will eat the ants' eggs and/or larvae. Nice.
Extatosoma tiaratum, is a kind of stick bug resembling dried thorny leaves as an adult and looking nothing like an ant, hatches from the egg as a replica of a Leptomyrmex ant, with a red head and black body. The long end is curled to make the body shape appear ant-like, and the movement is erratic, while the adults move differently, if at all. This affords the young E. Tiaratum protection against predators who mistake it's helpless form for a nasty, crunchy ant that would... if it could... knock your soda out of your hand and make you lap it up off the floor while all his ant buddies laughed.