Leafcutter Ant (Atta cephalotes) Fact Sheet: Reproduction & Development

Few colony members breed

• Typically, a single reproductive queen that mates with several males prior before founding a new colony (e.g., Hölldobler and Wilson 1990; Hölldobler and Wilson 2011; Muñoz-Valencia et al. 2020)
  • Queen mates once, before founding a new colony
    • See Courtship
  • Several thousand males develop per year in mature colonies, but are short-lived
  • Workers (queen’s daughters) sterile (e.g., Dijkstra and Boomsma 2006)
• Some instances of dual maternity and more variable breeding systems (Sundström et al. 2005; Sotelo et al. 2015; Muñoz-Valencia et al. 2020)
  • Where two queens, unclear if live in same nest or due to replacement of a previous queen

Mating

• Young winged females and males depart each year on mating flights (Brent 1886; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Synchronized flight among colonies in the same area
  • Disperse to mate and establish new colonies (in case of females)
  • Males die after mating (Wirth et al. 2003; Hölldobler and Wilson 2011)
• Mating takes place high in the air (Hölldobler and Wilson 1990; Hölldobler and Wilson 2011; Ulrich Mueller, personal communication, 2022)
  • Sperm transferred in bundles through complex copulation structures (see Baer and Boomsma 2006)
• Females acquire and store sperm on a single mating flight for their entire adult life (Kerr 1962; Wirth et al. 2003; den Boer et al. 2009; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Queens highly efficient in use of stored sperm, only 1–2 sperm per egg for fertilization (den Boer et al. 2009)
    • Allows queens to fertilize millions of eggs, perhaps 500 million or more, over her lifetime
  • Sperm from different males compete with one another, but queens can stop sperm competition (e.g., den Boer et al. 2010; den Boer et al. 2015; Dosselli et al. 2019 [in Atta columbica])

Queen dispersal

• Mature Atta colonies produce several thousand reproductive females (alate queens) per year (e.g., Hölldobler and Wilson 1990; Hölldobler and Wilson 2011)
  • Each alate queen can potentially found a separate colony (but low survival rates)
• Queen carries a small piece of mycelia with her to grow fungus gardens at new colony location (e.g., von Ihering 1898; Bailey 1920; Weber 1972b; Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Carried in pouch in mouth cavity located below esophagus (infrabuccal pocket)
• Queen’s wings fall off after dispersal (mating flight) (Brent 1886; Hölldobler and Wilson 2011)

Colony establishment

• Queen excavates single nest chamber (e.g., Weber 1972b; Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
• Queen spits out stored fungus piece (see above), a “starter” to grow fungus gardens at new colony site (Bailey 1920; Autuori 1956; Weber 1972b; Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Fungus fertilized by queen’s excretions and eggs
  • Queen does not feed on early fungus culture
    • Lives off her body fat and reabsorbed wing muscle tissue
• Queen cares for fungus garden until enough eggs hatch and larvae develop into adult workers (Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
• Workers then take on nest care duties and begin foraging outside the nest (about a week after nest founding) (Wilson 1983; Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Gradually take on all duties of the colony, later adding excavation of more nest chambers and colony defense

Colony maturation

• Queen fed, groomed, and protected by her daughter workers (Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
• Queen’s egg laying increases (Hölldobler and Wilson 1990; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • Lays many eggs — more than 25,000 per day in a mature colony — until death
  • Workers distribute eggs throughout fungal gardens
• Atta colony growth slow during first 2 years (Hölldobler and Wilson 1990; Hölldobler and Wilson 2011)
  • Also see "Colony survival rates"

Brood care

• Small workers tend larvae and pupae (Weber 1972b; Hölldobler and Wilson 1990; Hölldobler and Wilson 2011)
  • Immature ants housed in fungus gardens
• See Social Structure
• See Diet

More research needed

• Atta cephalotes queens among the longest-lived insects (Keller and Genoud 1997; Hölldobler and Wilson 2009; Hölldobler and Wilson 2011)
  • May live 10–20 years or longer
• However, in observations of 40 wild nests in Brazil, Meyer et al. (2009) found an average colony life span of about 8 years — lower than estimates based on colonies in managed care
  • Swanson et al. (2019) state that Atta nests more dynamic than previously thought; scientific studies needed to track nests spatially, from founding to collapse
• Sperm depletion may be a significant cause of mortality of mature Atta colonies (den Boer et al. 2009)
  • The average Atta columbica queen has stored sperm to last almost 9 years of normal colony development
  • Also see "Mating"

Colony survival rates

• Year-to-year nest densities stable (Meyer et al. 2009)
• Highest mortality in early months of colony founding, due to pathogens and predators (Hölldobler and Wilson 1990; Perfecto and Vandermeer 1993; Hölldobler and Wilson 2011)
  • Fowler et al. (1983) found only 10% of colonies survived the first few months after founding

Predators

• Dispersing queens preyed on heavily, due to nutrient-rich gaster (abdomen) (Ulrich Mueller, personal communication, 2022)
  • Birds
    • Members of nightjar family (Caprimulgidae) feed on Atta texana (mates at dawn, like A. cephalotes)
  • Bats
  • Ground mammals
    • Many hunt for Atta queens as they begin digging a nest after mating flight
• Army ants (e.g., Swartz 1998; Rao 2000; Hölldobler and Wilson 2011)
  • Prey on brood young and hinder establishment of colonies
• Possibly bullet ant (Paraponera clavata) (Wetterer 1994)

Diseases (non-comprehensive list)

• See Managing Gardens

Parasites (non-comprehensive list)

• Parasitic flies (Diptera: Phoridae) (Eibl-Eibesfeldt and Eibl-Eibesfeldt 1967; Orr 1992; Feener and Brown 1993)
  • Also see "Defense"

A gardening ant carries a brood chamber.

Larval brood chambers are woven into the fungus garden structure. Workers cooperatively care for developing larvae and pupae.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

A winged Atta cephalotes.

The vast majority of individuals in an Atta colony do not reproduce. But each year, a few thousand winged females and males disperse to mate.

Mated females then attempt to found new colonies, though most do not survive. A new queen's wings fall off after dispersal.

Young queens take a small piece of fungus with them to grow fungus gardens (food farms) at their new colonies.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.