California Havester Ant
California Havester Ants (Red Harvester Ants) prefer arid chaparral habitats and are native to the southwest United States. Nests are made underground (up to 2.5 meters deep) in exposed areas. Their diets consist primarily of seeds, and they consequently participate in myrmecochory, an ant-plant interaction through which the ants gain nutrients and the plants benefit through seed dispersal. Ant foraging is guided by chemical signals that lead the ants up to 50–60 km from the nest at times.Red harvester ants are often mistaken for fire ants, but are not related to any fire ant species, native or introduced.
Harvester ants will defend their colonies vigorously against real or perceived attacks, whether by large or small animals. They may bite ferociously and their stings are venomous and painful. The effect spreads through the lymphatic system, sometimes causing dangerous reactions, especially in animals sensitive or allergic to their venom.
Red harvester ant nests are characterized by a lack of plant growth and small pebbles surrounding the entrance to the tunnel, which usually descends at a pronounced angle. Hulls of seeds may however be found scattered around the nest. In grassland areas, such as ranches, the lack of plant life makes red harvester ant colonies very easy to spot, and where they are very plentiful they may make serious inroads into the grazing available to livestock.
The mounds are typically flat and broad. Three to eight trails typically lead away from the mound, like “arms”. These trails are used by ants to collect and bring food back to the mound. “Scout” ants are the first ones out of the mound every morning. They seek food, and mark their path as they return to the mound to alert the worker ants. The worker ants follow the scent trail and collect the food. Other worker ants clean, extend and generally tend to the mound, the queen and the brood. All the ants in the colonies are females apart from the winged males produced in the breeding season.
The main food source for red harvester ants usually consists of seeds, which they hoard in great numbers. The food is first ground to a bread-like consistency using the ant’s large mandible, and is then stored in in a granary, assuring the colony access to food year-round. Seed collection on behalf of the red harvester ants benefits their ecosystem through the process of myrmecochory, in which ants aid in the dispersal of seeds while foraging for food. Both plant and ant benefit from this relationship: the plants increase their dispersal range and density, while the ants benefit from acquiring nutrients and ensuring a more secure food supply in future harvests. This is typically understood as a mutualistic interaction. Dead insects are also collected during foraging.