An Interesting and Useful Chemical
Formic acid is an irritating chemical present in the sprayed venom of some ant species and in the secretion released from some stinging nettles. It's dangerous at high concentrations, but at low concentrations it's very useful. Humans use formic acid as a food preservative, since it's an antibacterial substance. It’s also used to kill pests, to produce food and cosmetic additives, and to help a variety of industrial processes to occur.
Our bodies make small quantities of formic acid from the methanol that we ingest, inhale, or produce. Some of the methanol produced in the body is made from the sweetener known as aspartame. The body converts aspartame into aspartic acid, phenylalanine, and methanol. The methanol is then converted into formic acid. Fortunately, researchers say that the formic acid in our body is generally too dilute to be dangerous.
hemical Structure and Properties
Formic acid is the simplest member of the carboxylic acid family. It's also known as methanoic acid. The chemical's molecular formula is HCOOH. The molecule is composed of a carboxyl group (COOH) with a hydrogen atom attached. In the carboxyl group, the carbon atom has a double bond joining it to the oxygen atom and a single bond joining it to the hydroxyl (OH) group, as shown in the illustration above.
Formic acid can be made synthetically in laboratories. In nature, it usually exists in the form of a colorless liquid. This liquid freezes at 8.3 degrees Celsius (46.9 degrees Fahrenheit) and boils at 100.7 degrees Celsius. (213.3 degrees Fahrenheit). It has a strong odor and is often described as having a "pungent" smell.
Yellow crazy ants are creating serious problems with the formic acid that they spray.
Yellow crazy ants are creating serious problems with the formic acid that they spray.
Forest and Kim Starr (USGS), via Wikimedia Commons, public domain image
Formic Acid in Ants
Formic acid got its name from “formica”, the Latin name for ant. An English naturalist named John Ray was the first person to isolate an acid from ants. In 1671, he distilled the crushed bodies of the dead insects to extract the acid, which was eventually named formic acid.
Ants bite to protect themselves or to attack other creatures. They grab hold of their victim with their mandibles (jaws). Some species then sting the victim. The stinger is located at the tip of the abdomen and injects a toxic secretion. Instead of stinging, some ant species release a spray of venom from the end of their abdomens. This venom contains formic acid. Some ants bite but do not sting or spray toxic chemicals.
Instead of a stinger, members of the ant subfamily known as the Formicinae have an opening at the tip of their abdomen called an acidopore. The acidopore releases a spray of formic acid from the ant's venom gland when necessary. Wood ants, yellow crazy ants, and tawny crazy ants all belong to the Formicinae subfamily.
Thousands of Wood Ants Spray Acid
Yellow Crazy Ants
Yellow crazy ants (Anoplolepis gracilipes) are invasive and very destructive insects. They neither bite nor sting, but they do spray formic acid to subdue their victims. The ants are yellow-brown in color and have long legs and antennae. They're known for behaving frantically when they're disturbed.
Yellow crazy ants are versatile creatures. They eat a wide variety of animal tissue as well as honeydew secreted by aphids and other insects. The ants are classified as predatory scavengers. A very worrying aspect of their lives is the ability to form huge supercolonies that have hundreds of queens.
The insects have caused some serious damage to the populations of some animals, including the red crabs on Christmas Island and seabirds in Hawaii. They also interfere with human lives. Sometimes the ant population releases so much formic acid into the air around their nest that breathing becomes painful. Skin and eye contact with the acid is also painful.
Like the yellow crazy ant, the tawny crazy ant releases a spray of formic acid as a chemical weapon. It also rubs its formic acid secretion over its body. The covering of acid protects it from the venom of the red imported fire ant. How this protection works is unknown.
