Strumigenys is a diverse genus in North America with almost 50 species. Despite this diversity though, the genus is almost exclusively encountered by Myrmecologiests and those in other scientific fields that involve sifting through leaf litter and dead wood.
For better close ups, here's a link to Ant Web's specimens, and Alex Wild's album of the genus. Notice the odd petal-like structures that cover the body. These are modified hairs which I believe are used help cloak the ants as they hunt. Some species in the genus have long mandibles similar to a Trap Jaw ant's. These are used to allow oils (and fungi?) which make the ant less noticeable while hunting.
They're primarily predators of springtails which are small, mite or termite-looking insects often found in decaying wood. Truthfully though these ants are more than happy to kill any sort of soft bodied invertebrate.
These ants require "cool" conditions in order to survive. In the wild they always nest inside the damp and decaying media within the hollow of a tree, or in a soggy log that's often well shaded and rotting. Other species are at home nesting in soil and leaf litter, but good luck finding those. Colonies do not make mounds of any kind, entrance holes are often cryptic at best, and populations tend to range around 200 individuals that could happily fit on a US. Quarter.