ure 3) occur within the underground nest and are only seen when nests are disturbed or when they are being carried to a different location by workers (Figure 4). The eggs are small but can be seen with the unaided eye. They hatch into the grub-like legless larvae that are fed by the workers. Ant larvae in general are legless, carrot shaped with a well-developed unpigmented head capsule and are typically hooked at the head end. The larvae will grow and molt (shed their exoskeleton) 3 times prior to molting into the pupae, which are similar in appearance to the adults except that their legs and antennae are held tightly against the body. As with the larvae the pupae lack pigmentation, especially in the early instars. As they mature they begin to turn darker. As discussed in honeybees, the function of the polymorphic workers is determined primarily by age (and to a much lesser degree by size). Younger workers typically care for and feed the brood while middle-aged workers maintain and protect the colony. The oldest workers forage for food.
Figure 3. Egg, larval and pupal stage of fire ants. Image courtesy of USDA Archives.
Figure 4. Worker fire ants carrying larva for relocation. Image courtesy of USDA, Calif. Dept Agriculture.
The alates, or winged reproductives (Figure 5), are most abundant in the late spring and early summer, but can be found at any time of the year. The males are decidedly smaller than the females, glossy black and have a smaller head. Although both winged males and females can be found in the same colony, as a general rule one form will be dominant. It is possible that this functions to increase the chances of one sex mating with another from a different colony. Most colonies in a given area typically swarm on nuptial flights at the same time. This benefits the species and insures mixing of the gene pool. It is well-documented that inbreeding is generally detrimental to a given species.
Figure 5. A winged reproductive of the red imported fire ant. Image courtesy of USDA Archives.
Mating flights most often occur at mid-morning 1 or 2 days following a rainfall if the temperature is above 22°C and the wind is light. At this time a virgin female flies into a cloud of congregating males and mates in the air. The male subsequently dies while the female seeks a location to start a new colony. Once located, she breaks off her wings and excavates a brood chamber approximately 1 to 2 inches below ground. The new queen subsequently deposits a few dozen eggs which hatch in a little over a week. The queen does not forage but feeds the first generation of larvae from nutrients obtained from her fat reserves and by dissolving her no longer needed wing muscles. The larvae obtain the nutrients by trophollaxisis (exchange of alimentary fluids) or from sterile eggs she has produced for that purpose. The entire life cycle is completed in 3 to 4 weeks.
The initial generation of adult worker (minims) are relatively small due to a limited amount of nutrients available from the queen. Once developed these worker open up the brood chamber and begin to forage for available food. Soon another generation of larger adult workers has developed and the colony begins to grow. Workers start to emerge daily and within 6 months the colony population approaches several thousand and an above ground mound is visible. The polymorphic (poly in Latin means many and morph means form) nature of the worker becomes more apparent. The largest workers in the colony (majors) can be as much as 10 times the size of the smallest workers (media). The queen lives up to 7 years and produces an average of 1600 eggs per day. At maturity, a monogynous (one queen) fire ant colony can consist of over 250,000 ants. As discussed above some fire ant colonies have only one queen per nest while others can have many queens and are called polygynous colonies. The polygynous colony may be more difficult to control because all the queens must be killed to prevent the colony from surviving. Polygynous colonies frequently expand by "budding"; i.e., some of the queens and