Solenopsis invicta have developed many characteristics over time that have helped them to overcome the hurdles they face in their daily lives. Complications such as RIFA pen drawing, photo credit to Joe MacGown, Mississippi Entomological Museum changes, predation, and competition leave a great impact on the life of the RIFA which is why they have developed adaptations over time to better help them survive. In general, the ants that are designated “workers” range from 1/16th to 1/5th inches long. What distinguishes these ants from others is their reddish body color along with the dark brown gaster (the last abdominal segment) and, of course, the stinger. They have large eyes and three teeth on the front of their head. Other morphological characteristics include ten segmented antennae, a petiole (which is the section adjacent to the gaster) with two nodes, and an absence of spines on the thorax (Greenberg et al. 2012).
       It has been found that the antenna of this species of ant contains chemosensory proteins which are thought to be involved in chemical signaling transmitted by the ants. One particular chemosensory protein is conveyed in the worker antennae and has led biologists to believe that there is an underlying olfaRIFA worker head with antennae, photo credit to Joe MacGown, Mississippi Entomological Museum function (Gonzalez et al. 2009). S. invicta have antenna that are ten-segmented, with two-segmented clubs at each end. The Red Imported Fire Ants depend on communication between one another, and the antenna is a key channel of sensory input they use. Each antennae possess receptors for “volatile odors and pheromones, contact chemoreception, water vapor, carbon dioxide, sound, proprioception, and touch” (Renthal et al. 2003). Biologists have also discovered that the antennae are “sexually dimorphic,” meaning that the male and female antennae vary due to their differing roles in a colony. The male antenna are relatively simple due to the fact that the male ants do not participate in foraging or take care of the brood like the females.
       Furthermore, the morphological feeding structures of the adult ants have been especially advantageous in their mission of finding and consuming the proper nutrition needed for them to survive. S. invicta have chewing mouth parts with mandibles that are adapted to bite, slice, and rip solid food apart and, alternatively, aid in nest maintenance, defense, and construction. Their mouthparts also possess a pre-oral cavity that is used as a “food receiving pocket.” Added to that, the ants also grow ridges and hairs along the mouth cavity in order to sift out particles and debris from the liquids they consume. The particles are compacted into pellets that later can be discarded (Klotz et al. 2008).
       One of their most well-known adaptations, however, is their venomous sting that many humans have had the displeasure of experiencing on a first hand basis. ThRed Imported Fire Ant stinging a human, photo credit to Alexander Wilde Red Imported Fire Ants are at risk for predation due to their relatively small size compared to the other organisms they encounter. As a solution to this problem, the RIFA inject a “necrotizing, alkaloid venom” into those who threaten them. Most of the venom is composed of these alkaloids, which are the cause of not only the pain, but also the white abscess that one can expect to see approximately a day after the stinging incident. The rest of the venom is made up of a mixture of proteins and other small molecules that can produce an allergic reaction in hypersensitive individuals. When a fire ant mound is disturbed, for example with a shoe, many ants will rush out of the nest and crawl up the shoe very quickly stinging the intruder. This is accomplished when the worker ants attach to their victims with their mandibles and then lower the tip of their gaster in order to inject the venom through the stinger and into their target. This particular species of ants not only bites but stings as well (Collins and Scheffrahn 2001).
       Other fascinating characteristics of the RIFA include the way in which they reproduce along with their life cycle. You can learn more specifics regarding the reproduction of the Red Imported Fire Ant by clicking here.

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