Yes, diatomaceous earth is indeed effective in killing ants. When viewed under a microscope, diatomaceous earth is actually made out of millions of microscopic particles, not unlike shards of glass, that are sharp enough to penetrate and puncture the relatively soft inner parts of invertebrates.
Comprised mostly of silica, diatomaceous earth is in fact the fossilized remains of plankton from many, many years ago. Like other insects, ants have exoskeletons, which means that their hard external coverings also double up as skeletons as they have no internal skeleton. Diatomaceous earth works to kill any organism with an exoskeleton by penetrating the hard external shell, puncturing the insect, and then causing death by dehydration.
Though this may sound like a particularly grisly end, have no fear – diatomaceous earth is harmless to mammals even if consumed. In fact, some of our food contains diatomaceous earth to keep it free of bugs. Diatomaceous earth is commonly found in grains and other dried foodstuffs that may attract pests. Its efficacy in killing pests, combined with its relative safety to humans, makes it a great choice as a pest killer in many instances.
However, diatomaceous earth can get messy. Sprinkling and then cleaning it up can be a bothersome task. Excellent alternatives exist in the form of natural insecticides and repellants that are free of all harmful chemicals, yet are effective and way easier to use. The line of insecticides and repellents from EcoVenger® are pet-safe, child-safe, and more convenient than clumps of diatomaceous earth.