Strumigenys

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Strumigenys is a genus of small ants in the subfamily Myrmicinae. There are more than 880 species, making it one of the most diverse ant groups. Many Strumigenys ants have specialized trap-jaw mandibles and are active predators of tiny arthropods.

Diet and hunting
Most Strumigenys ants eat small arthropods, especially springtails, but they can also lap up sugar from nectar sources in some situations. They typically hunt alone, picking prey from leaf litter, soil, or dead wood. Some species forage in trees or nest inside other materials.

Nesting and lifestyle
Nests occur in a variety of places, most often in soil, under rocks, or under dead wood. Some nests are built under bark or among epiphytes. While many Strumigenys ants nest on their own, others live alongside larger ants, a situation called xenobiosis, or form social parasitic relationships.

Interactions with other ants
Strumigenys species show interesting relationships with other ants. For example, S. maynei lives in the nests of Platythyrea conradti and hunts within that nest, sometimes helping defend it. Strumigenys arizonica lives inside the nests of Trachymyrmex arizonensis and feeds on prey there. Some species are facultative nest associates, like S. pergandei, which can be found in nests of larger ants or living independently. There are also parasitic species, such as S. yaleogyna, which lives in the nest of its host Strumigenys loriae, and S. xenos, a workerless parasite of S. perplexa.

Mouthparts and diversity
Strumigenys ants show a lot of variation in mouthparts. Many are known as trap-jaw ants, with a special mechanism that snaps their jaws shut very quickly when triggered by sensory hairs. Mandibles come in different forms, including gripping, short-trap, and long-trap types, and these forms have evolved multiple times within the group.

Geography and habitat
Strumigenys is found worldwide, but most species live in tropical forests where leaf litter is abundant. The genus is especially diverse in the tropics, though some species occur in temperate regions.

Distinctive features
A common but distinctive feature in many Strumigenys is a spongiform, honeycomb-like tissue on the front part of the metasoma (the rear body segment). This tissue is thought to be connected to exocrine glands, though its exact function is not fully known. The ants also often have uniquely bent or bulbous setae (hairs) and a reduced number of antenna segments (four to six), with simplified palps.

Taxonomy notes
Strumigenys was established as a genus in 1860 by Frederick Smith. It contains hundreds of species and has many historical synonyms, including Pyramica, which has been moved in and out of synonymy with Strumigenys as scientists studied mandible and mouthpart morphology and, more recently, genetics.

In short, Strumigenys is a large, globally distributed group of tiny, predatory ants known for their trap-jaw jaws, diverse lifestyles, and interesting interactions with other ants in their ecosystems.