Leaf Cutting Ants in Captivity, Advice and notes from Randy

[Acromyrmexbob]

Taken from Natural History Notes, Captive Management, Atta,Randy Morgan

The basic husbandry requirements of all Atta species appear to be virtually identical (Morgan 1991b, 2001). Captive Atta colonies are extremely adaptable. They are typically maintained on fresh and processed plant materials that are not available to them in nature. They also can thrive in an endless variety of containment and nesting situations as long as their basic environmental requisites, especially humidity and temperature, are met.

It can not be overemphasized that the needs of the fungus gardens are much stricter than those of the ants, thus the primary husbandry goal is to focus on maintaining an optimal environment for fungal growth. This is best accomplished with a garden chamber design that both enhances and helps the ants regulate fungal microenvironment. The shape and size of garden chambers are relatively unimportant. Given an optimal environment, the ants will readily grow their fungus in any small protective cavity. Indeed, rapidly growing colonies will even sometimes construct fungus gardens in relatively exposed sites (pers. obs.).

Conventional Housing and Containment: Weber (1972, 1976) employed small, clear acrylic plastic containers, called garden chambers, to house an Atta colony and its fungus gardens. The clear containers allowed monitoring of fungal growth and observation of colony activities.

To accommodate an expanding colony, garden chambers were linked together with tunnels made from clear tubing. Interconnecting tunnels can be almost any length, but an optimal width is about 2.5 cm (1 in) in diameter. Wider passageways may be used by the ants as gardening sites, while much narrower tunnels restrict the free flow of workers and substrate. Plant material was placed in a separate container, called the foraging arena, also connected to the nest with tubing.

In such a system, where garden chambers and foraging arena are not otherwise contained, it is crucial that all components be extremely well constructed and fit precisely. The ants are adept and relentless chewers, will eventually open and escape from any small space, and begin to forage outside of their enclosure. Plastic sealant can be used to temporarily repair small cracks or holes used by escaping ants. A useful technique employed at the Insectarium involves first firmly-fitting the escape hole with small pieces of ultra fine (40-100 mesh/inch) stainless steel cloth (Table 1 lists source), which the ants can not chew through, then applying the sealant.

Insectarium Laboratory Housing: At the Insectarium, surplus or reserve colonies are maintained as small populations. Colonies are each housed within single glass-sided aquaria, which serve as foraging arenas, and in turn contain one or sometimes several garden chambers. We do not interconnect multiple garden chambers with tubing as all are contained within the overall foraging arena, and the workers readily move back and forth between nest chambers.

Foraging Arenas: Standard 19 or 38 liter (5 or 10 gal) glass aquaria are used to house and contain colonies residing in single garden chambers (Fig 11). Colonies can be kept relatively small and maintained this way for many years. If desired, larger tanks can be used for more populous colonies residing in several garden chambers. For example, our main back-up colony lives in a 151 liter (40 gal) tank housing six garden chambers.

To deter escape, all silicon sealant in the inner corners of the aquaria, which can give ants a foothold, is meticulously removed with a straight-edged razor blade. Then, to create a slippery barrier, about a 15 cm (6 in) wide band of 3-in-One multi-purpose oil is applied to the glass around the upper inner tank perimeter at weekly intervals, or more frequently if needed (Table 1 lists oil manufacturer and usage notes).

Garden Chambers: Small clear acrylic boxes are modified to serve as garden chambers (Figs 10-12; Table 1 lists source and specifications). For moisture control, each garden chamber is fitted with a 2 cm thick base layer of Hydrostone (Fig 10; Table 1 lists manufacturer and usage notes). Cured Hydrostone is porous and absorbs water, acting both as a moisture reservoir and to wick away any excessive condensation. The plastic bottom of the garden chamber is drilled with four 12 mm (1/2 inch) holes, one near each corner, that extend part way up into the Hydrostone base layer to allow for drainage.

While not essential, we usually cut and fit a rectangular piece of 8-mesh/inch hardware cloth (Table 1) to lay flush atop the Hydrostone base. This creates a thin spacer that slightly elevates the bottom of the fungus garden above a possible wet surface. We also add a small amount of tan mortar color (Table 1) to the Hydrostone during preparation to give it a natural earth tone.

Entrance Holes and Queen Exclusion: Each fungus garden chamber has a single entrance hole drilled in the box lid. This entrance hole is normally about 1 cm in diameter unless the box houses the queen. Then we create a slot-shaped entrance hole (about 4 x 15 mm) by drilling several overlapping holes in a line with a standard 11/64 inch drill bit and smoothing the edges. This opening (Fig 12) readily allows the passage of workers with plant material but not the queen, as per our USDA-APHIS-PPQ permit conditions.

Moisture Requirements: The fungus gardens need a constant, highly humid atmosphere, preferably at or near the saturation point (100% RH). Weber placed clean moist sand in containers housing small colonies, which have less ability to regulate moisture levels, but noted that sand was unnecessary for most large colonies with established gardens. A related problem is the accumulation of water within garden chambers from condensation, which is detrimental to the fungus if left unchecked.

The ants, in contrast, tolerate a wide range of humidity levels. They will survive in a dry atmosphere as long as they have access to drinking water. Weber recommended that humidity levels in the foraging arena be kept relatively dry (20-50% RH) to prevent the formation of molds. At the Insectarium, foraging arenas are kept a little more humid (50-60% RH) and regular debris removal eliminates mold problems. In a relatively humid atmosphere, plant material remains fresher longer and the ants require less or no drinking water.

At the Insectarium we do not always provide drinking water, especially for larger wellestablished colonies, but the provision of water can be advantageous for small colonies or during the drier winter months. When offered, drinking water is provided in shallow dishes or trays half-filled with course gravel, with the water level kept near that of the gravel surface, preventing the workers from slipping, falling in and drowning in deeper water.

Temperature Requirements: Ambient temperatures of 25-27ºC (77-80ºF) are ideal for fungal growth. Temperatures that are somewhat lower (20ºC; 60ºF) or higher (30ºC; 86ºF) are suboptimal for fungus grown in laboratory cultures (Weber, 1972). The ants, however, function well within a significantly broader range of temperatures. Their metabolism slows at cooler temperatures, and if briefly chilled in a standard household refrigerator (about 3ºC; 37ºF) they become torpid, but will recover when warmed. However, temperatures that are below freezing (0ºC; 32ºF) or above 35ºC (95ºF) are lethal to the ants.

Illumination of Observation Colonies: Atta colonies readily adapt to lighting at normal room intensities, and can have additional illumination to highlight the fungus gardens for public viewing provided that the gardens are not overheated. The type of lighting fixtures and their placement can be important considerations since florescent bulbs produce significantly less heat than incandescent bulbs. Observation nests should never be exposed to direct sunlight since this will quickly cause overheating and injure or kill the colony.

At the Insectarium, we illuminate our public display fungus garden chambers with two 75 watt incandescent floodlights shining down on the viewing windows from about 2 m (6 ft) away. This causes a several degree heating effect within the garden chambers, but since our building is maintained at about 24ºC (75ºF), the net result is an optimal temperature for fungal growth.

Seasonal Fungus Garden Management: Effective fungus garden management is the key to successfully keeping Atta. Fungus gardens are routinely monitored to distinguish healthy, actively growing gardens from ones that are shrinking or otherwise failing. Management practices are directed towards helping the ants maintain an optimal environment for fungal growth.

Seasonal variables may have a profound affect on management strategy. For example, in Cincinnati, spring and summer bring relatively high atmospheric humidity and moisture-laden plant material. Consequently, moisture potentially builds up within the garden chambers, and if this results in condensation and pooling, this excess moisture must be eliminated. Conversely, winter brings lower atmospheric humidity and reduced plant moisture, and garden desiccation must be prevented.

Garden chamber moisture levels are controlled by regulating moisture input and output. Excess moisture can often be regulated simply by a garden chamber design that provides adequate drainage. However, increasing ventilation (nest chamber openings) and offering relatively dry substrate can also be a part of the management strategy. Conversely, fungal garden moisture levels are often adequately maintained by vigorous colonies simply by providing them with moist substrate. However, hydrating the Hydrostone with water and reducing ventilation can also be useful in some situations.

Substrate Source and Use: It is vital that all plant material provided to the ants be free of insecticides, fungicides or other contaminants. While captive colonies often flourish even when fungal substrate choices are limited, we prefer to routinely vary the substrate to help ensure that a diversity of plant-based nutrients is potentially available to the fungus gardens. The source of the substrate we give to the ants is strongly dependant upon the season.

My own opinion is that 25-27C is a little high, mainly because of the possibility that any slight rise in temperature from this point would cause potentially irreparable damage to the colony. Lower temps, ie 23-25C allows for rises with a greater distance to travel before getting into difficulty. Good paper though.

[Andyj]

Nice read, did it come with the tables and illustrations ?

[Acromyrmexbob]

Nice read, did it come with the tables and illustrations ?

Yes but I didnt think you were ready for that much excitement. You can enter the title into the interweb and the original article will pop up. Its one of the wonders of the modern world, this new fangled net thingie.

[Andyj]

Your right the excitement was to much for me, i had to read this product twice " Mom’s Veggiewash " i'm glad i read it wrong.