21529150
not annotated - annotated - LINNAEUS only
The organization of foraging in the fire ant, Solenopsis invicta.
Although natural selection in ants acts most strongly at the colony, or superorganismal level, foraging patterns have rarely been studied at that level, focusing instead on the behavior of individual foragers or groups of foragers. The experiments and observations in this paper reveal in broad strokes how colonies of the fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), allocate their available labor to foraging, how they disperse that force within their territory, and how this force changes with colony size, season and worker age. Territory area is positively related to colony size and the number of foragers, more so during the spring than fall. Changes of colony size and territory area are driven by seasonal variation of sexual and worker production, which in turn drive seasonal variation of worker age-distribution. During spring sexual production, colonies shrink because worker production falls below replacement. This loss is proportional to colony size, causing forager density in the spring to be negatively related to colony and territory size. In the fall, colonies emphasize worker production, bringing colony size back up. However, because smaller colonies curtailed spring worker production less than larger ones, their fall forager populations are proportionally greater, causing them to gain territory at the expense of large colonies. Much variation of territory area remains unexplained and can probably be attributed to pressure from neighboring colonies. Boundaries between territories are characterized by "no ants' zones" mostly devoid of fire ants. The forager population can be divided into a younger group of recruitable workers that wait for scouts to activate them to help retrieve large food finds. About one-third of the recruits wait near openings in the foraging tunnels that underlie the entire territory, while two-thirds wait in the nest. Recruitment to food is initially very rapid and local from the foraging tunnels, while sustained recruitment gradually involves the recruits waiting in the nest. As recruits age, they become scouts searching for food on the surface, and die about two weeks later. Foraging tunnels decrease in cross-sectional area with distance from the nest, in keeping with the gradual bleeding off of workers to the surface with distance. Foragers lack route-faithfulness, and having been marked and released at one point within the territory, they can be recaptured at any other point a day later. The size of the territory actually occupied may be limited during dry weather, resulting in very large no-ants' zones.
Ann file
T1 Species 46 64 Solenopsis invicta
N1 Reference T1 Taxonomy:13686
T2 Species 401 419 Solenopsis invicta
N2 Reference T2 Taxonomy:13686
T3 Out-of-scope 427 438 Hymenoptera
N3 Reference T3 Taxonomy:73399
#1 AnnotatorNotes T3 TODO: check
T4 Species 36 44 fire ant
N4 Reference T4 Taxonomy:13686 Solenopsis invicta
T5 Species 391 399 fire ant
N5 Reference T5 Taxonomy:13686 Solenopsis invicta
T6 Species 1661 1670 fire ants
N6 Reference T6 Taxonomy:13686 Solenopsis invicta