Pseudomyrmex ferruginea

The acacia ant (Pseudomyrmex ferruginea) is a species of ant of the genus Pseudomyrmex. These arboreal, wasp-like ants have an orange-brown body around 3 mm in length and very large eyes. The acacia ant is best known and named for living in symbiosis with the bullhorn acacia (Acacia cornigera) throughout Central America. The ant and the acacia exemplify a coevolution of a mutualistic system, as described by evolutionary ecologist Daniel Janzen. P. ferruginea is an obligate plant ant that occupies at least five species of acacia (A. chiapensis, A. collinsii, A. cornigera, A. hindsii and A. sphaerocephala). Its life cycle conforms to the claustral pattern of ants in general. To repel herbivorous animals, various acacias protect their succulent leaves with one of several methods, including vicious-looking spines, repellent, noxious chemicals, and as in the case of the bull's horn acacia by developing a mutualism with the Acacia ant. The symbiotic relationship begins when a newly mated queen is attracted by the odour from the tree and starts nesting inside the large hollow acacia thorns. The queen nibbles into the thorn to lay 15–20 eggs to produce the first generation of workers. As the colony grows, more of the bulbous thorns get inhabited, and when the colony reaches some 400 individuals the ants start to act as gardeners. As gardeners, the ants aggressively attack creatures of all sizes attracted by the acacia leaves, killing insects such as crickets and stinging the heads of mammals such as goats. Even other plants such as epiphytic vines are repelled and as little as an unfamiliar odour can cause the ants to swarm toward the potential threat. Additionally, the ants scout the ground around the tree for seedlings and destroy any competitors they find. In compensation, special glands at the base of the tree's leaves produce a nectar rich in sugar and amino acids, and the tips of the leaves sprout Beltian bodies, small nutritious packets of oils and proteins.