Mycocepurus goeldii

Mycocepurus goeldii

Mycocepurus goeldii is a small fungus-growing ant native to South America, where it ranges from Brazil through Bolivia, Paraguay, and into northern Argentina ^[1]. Workers are monomorphic (all the same size) and measure around 2-5mm ^[2], making them one of the smaller attine ants. This species is the largest in the Mycocepurus genus and can be identified by its distinctive spine pattern on the mesosoma (middle body section) ^[1]. Colonies build elaborate underground nests that can reach nearly 2 meters deep, with multiple chambers housing their fungal gardens ^[1].

What makes M. goeldii particularly interesting is its social flexibility, it's one of the few fungus-growing ants that can form either single-queen or multi-queen colonies ^[3]. This species also serves as a host for the workerless social parasite Mycocepurus castrator, which invades colonies and suppresses the host's reproductive output ^[4]. Unlike leaf-cutter ants that use fresh leaves, these ants cultivate their fungus on decomposing plant matter, insect feces, and other organic debris they collect ^[5][6].

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Native to South America, found across Brazil, parts of Bolivia, Paraguay, northern Argentina, Colombia, Guyana, and Panama. Inhabits diverse environments from Amazon rainforest to savannah (Cerrado) and agricultural areas ^[1][7]. Does not occur in elevated mountain regions of the Andes ^[1].
• Colony Type: Facultatively polygynous, colonies can have a single queen or multiple queens (up to 4 documented). In the Brazilian Amazon, both types occur, in some populations near São Paulo, colonies tend to be single-queen ^[1][8].
  • Colony: Optionally polygyne
  • Founding: Claustral
• Size & Growth:
  • Queen: Estimated 5-7mm based on genus patterns
  • Worker: 2-5mm ^[2]
  • Colony: 100-1,500 workers ^[9][6]
  • Growth: Moderate, based on lower attine patterns
  • Development: Estimated 5-8 weeks at optimal temperature based on related lower attine species (Direct development data unavailable, estimates based on genus-level patterns for basal Attini)
• Antkeeping:
  • Temperature: Keep at 24-28°C. As a Neotropical species from Brazil, they prefer warm conditions. Avoid temperatures below 20°C.
  • Humidity: Moderate to high. Native to humid rainforest and savanna environments, keep nest substrate consistently moist but not waterlogged. Provide a gradient with slightly drier areas for the ants to choose.
  • Diapause: No, being tropical, they do not require hibernation. However, slight seasonal slowdown may occur in cooler months.
  • Nesting: Y-tong (acrylic) or plaster nests work well. These ants are substrate farmers and need space for their fungus garden. Provide deep nesting areas since wild colonies can reach 190cm deep ^[1]. A naturalistic setup with soil chambers mimics their natural nesting preferences.
• Behavior: Generally peaceful and non-aggressive. Workers forage individually for organic matter to feed their fungus garden rather than forming large foraging columns. They are small but active, and because of their size, escape prevention should include fine mesh barriers. Workers are fungivores, they don't hunt large prey but maintain their fungal crop. They may accept small protein sources like fruit flies or tiny insects. They are not known to sting and pose no danger to keepers.
• Common Issues: small size means escapes are likely without fine mesh barriers, colonies can be sensitive to mechanical disturbance that affects their fungus substrate, social parasite Mycocepurus castrator exists in the wild, wild-caught colonies may be parasitized, requires consistent moisture for fungus health, drying out can be fatal, slow founding phase, queen may take months to raise first workers

Nest Preferences and Housing

Mycocepurus goeldii nests in soil, often with rotten wood or organic debris near the entrance. Wild colonies excavate deep nests reaching nearly 2 meters below the surface, with individual chambers averaging 35cm deep ^[1][6]. Each colony typically has 4-21 chambers, with about half containing fungus gardens ^[10][6]. Chamber volumes average around 629cm³, and the fungus gardens are typically laminar sponges suspended from the chamber ceiling ^[6].

For captive care, a Y-tong (acrylic) nest or plaster formicarium works well. Provide deep enough chambers to accommodate their natural tendency to build multiple levels. The nest should have areas of moist substrate for the fungus garden and slightly drier areas where ants can retreat if conditions become too wet. Because they cultivate fungus, the nest material should be able to hold some moisture without becoming waterlogged. A small water reservoir or moisture gradient helps maintain the humidity they need. Test tube setups can work for founding colonies but will need upgrading as the colony grows.

Feeding and Diet

As a lower attine (basal fungus-growing ant), M. goeldii has a different diet than leaf-cutter ants. Instead of cutting fresh leaves, they cultivate their fungus garden on partially decomposed organic matter. In the wild, they primarily use insect feces, fruit pulp, seeds, flower remains, and even bird or insect excrement as substrate for their fungus ^[5][11][6]. They also collect highly decomposed leaf litter ^[12].

In captivity, you can feed the colony small amounts of organic matter like fruit scraps, crushed insects, or specialized ant food formulated for fungus-growers. The key is providing variety, they need different substrates to maintain a healthy fungus garden. Some keepers report success with tiny fruit flies, small pieces of fruit, or even small amounts of honey water (though this should be offered sparingly and removed if not consumed). The fungus garden is their primary food source, so maintaining its health is critical. Avoid overfeeding protein-rich foods that could harm the fungus.

Temperature and Seasonal Care

Being a Neotropical species from Brazil and surrounding countries, M. goeldii prefers warm temperatures in the range of 24-28°C. They are found in diverse habitats from Amazon rainforest to Cerrado savanna, all of which maintain relatively warm year-round temperatures ^[1]. Avoid exposing them to temperatures below 20°C for extended periods.

Unlike temperate ants, they do not require a true hibernation period. However, slight seasonal variations in activity may occur, colonies may be less active during cooler months even indoors. If you keep room temperature in the low-to-mid 20s°C, they should do well year-round. A heating cable on one side of the nest can create a temperature gradient, allowing ants to choose their preferred spot. Just be careful not to overheat or dry out the nest.

Colony Structure and Reproduction

One of the most interesting aspects of M. goeldii is its flexible colony structure. This species is one of the few fungus-growing ants that can form either single-queen (monogyne) or multi-queen (polygynous) colonies ^[3]. In the Brazilian Amazon, both types occur in the same area, while populations near São Paulo tend to be primarily single-queen ^[8].

Colony sizes range from about 100 to 1,500 workers ^[9][6], with an average of around 319 workers in studied wild colonies ^[6]. Nuptial flights occur seasonally, typically starting around October in the Amazon region. During this time, workers dramatically modify the nest mound, creating 20-30 entrance holes that give the mound a sponge-like appearance ^[13][14]. After mating, workers close the extra entrances, returning to a single entrance. Queens may mate with multiple males (polyandry), with documented mating frequencies of up to 4 matings ^[15].

Behavior and Defense

M. goeldii workers are small but active and generally peaceful. They don't exhibit aggressive swarming behavior like some larger attines. Their primary defense is staying underground and avoiding confrontation. Workers are not known to sting, and due to their small size, even if they could sting, it would not penetrate human skin.

Foraging occurs individually or in small groups, with workers collecting organic debris to bring back to the nest for fungus cultivation. They are not aggressive defenders and pose no danger to keepers. However, because of their small size, they can escape through tiny gaps. Excellent escape prevention with fine mesh is essential, even small gaps in tubing or lid seals can allow escapes.

One notable behavior is their nest modification during mating season, when workers create multiple entrances. This is normal seasonal behavior and not a cause for concern. ^[13][14]

Common Problems and Health

Several issues can affect M. goeldii colonies in captivity. The most critical is maintaining the fungus garden, if the fungus dies, the colony will not survive. This means avoiding sudden changes in humidity, temperature extremes, and contaminated substrate. Keep the nest consistently moist but never waterlogged.

Mechanical disturbance can also impact them, they are sensitive to vibrations and nest disturbances that might damage their fungus gardens ^[16]. When working with the colony, be gentle and minimize disruption.

Wild-caught colonies may be parasitized by the social parasite Mycocepurus castrator ^[1]. If your wild-caught colony shows unusual behavior (no sexual brood, strange queen behavior), parasitism is a possibility.

Finally, their small size makes escape prevention critical. Use fine mesh on all openings and check connections regularly.

Frequently Asked Questions

References