Diapause in Ants:
A Guide for Ant Keepers

Ants are fascinating species, and many people enjoy keeping them as pets in their homes. But unlike other pets, ants can go through a period of dormancy called diapause. Diapause is a natural process in many ant species during the winter and is essential for survival. In this guide, we'll explain diapause, why ants enter this state, and how to care for them during this time.

To properly put your ant colony into diapause, it is essential to follow a specific process to ensure the survival of your ants. Inducing diapause in captive ant colonies is a valuable practice for the health and well-being of the ants. Proper planning, understanding the specific requirements of each species, and monitoring the colony during diapause are critical to a successful diapause period.

Ant on snow during winter diapause similar to hibernation

What is Diapause?

Diapause is a physiological state characterized by slowed metabolism, which ants enter during the late fall and winter seasons to conserve energy and endure adverse environmental conditions. The queen stops laying eggs, and the workers begin to aggregate more and develop large fat bodies, which can be seen as their gasters (abdomens) swell in size. The workers also produce glycerol, an alcohol that helps prevent the formation of ice crystals within the ants’ bodies.

Diapause or Hibernation?

Diapause is the proper terminology for ants during winter, not hibernation. While hibernation refers to a period of extended sleep, diapause is a period of suspended development or dormancy in which the growth cycle stops and the ant enters a state of rest. Unlike hibernation, growth does not continue during diapause.

Why do ants go through diapause?

Ants enter diapause to survive periods of unfavourable conditions, such as cold temperatures, droughts, or food shortages. This allows them to conserve energy and resources until conditions improve. It also allows them to survive through the winter, as many ant species cannot withstand freezing temperatures.

This implies that under certain trigger conditions, such as abrupt temperature drops or food scarcity, ants may enter a state of diapause at any time during the year, adapting to environmental challenges.

Do my ants need diapause?

Not all ant species undergo diapause. Usually, ant species of temperate and Mediterranean origins undergo diapause. If you are keeping temperate ants, most likely, your ants will undergo diapause in the winter. In contrast, tropical ants do not undergo diapause in winter.

Ants in the wild gradually prepare for winter (diapause) through seasonal temperature changes. However, ants kept in captivity must be artificially introduced to diapause to keep them healthy. Camponotus species, for example, seem to be highly reliant on temperatures for their well-being.

What happens to the ants during diapause?

Before diapause, the ants will start to build up energy reserves in their bodies so that they can survive the winter without food. In most temperate species, the workers will stop foraging for food and become inactive, while the queen will rest and stop laying eggs. The larvae will stop growing. Because their activities are greatly reduced, they can survive with their energy reserves for a few months. Some Mediterranean species do not completely stop foraging and will still require food during diapause.

Can I stop my ants from entering diapause?

You can stop your ants from entering diapause by preventing the temperature of the nest from dropping during winter, but this is not recommended. Diapause is a natural need of ants and skipping it can result in slower colony growth, smaller workers, and a shorter lifespan in the long run. Certain ant species will enter diapause even if the temperature is not dropped, and it is controlled by their biological clock.

Will eggs, larvae and pupae survive?

Ant eggs and pupae are unlikely to survive diapause, as they will not be able to withstand the cold temperatures. Therefore, it is recommended that ant hobbyists ensure that the pupae have eclosed into workers and the eggs have hatched into larvae before starting the diapause process. Additionally, in some species with a delicate schedule, it is imperative to initiate diapause in a timely manner. For these species, removing any undeveloped pupae may be necessary in order to prevent harm to the colony.

Do queens overwinter without laying eggs?

Some species of ants have a reproductive strategy where the newly fecundated queen ant will overwinter (go through diapause) without laying eggs and begin to lay eggs in the following spring when environmental conditions become more favourable. This allows the first workers to survive through winter conditions and ensures a good start to the colony. During the overwintering period, the queen will remain inactive and conserve energy, waiting for the conditions to become favourable for egg-laying and colony growth.

Examples of queen ants that exhibit this behavior include Crematogaster cerasi, Lasius neoniger, and Lasius brevicornis, among others.

How long and when, & can it be skipped?

Typically spanning 3 to 5 months, the duration of this process may vary across species. However, a standard diapause period is observed to be four months, aligning with the harsher climatic conditions of winter.

For example, in the northern hemisphere with temperate species, ant-keepers induce diapause between October to February or November to March. On the other hand, species that need a minimum of two months or 60 days can do it between December to January.

As a general rule, ants need a minimum of 60 days at a constant temperature below 15°C before they can exit diapause. Without the cold temperatures and a gradual transition back to warm temperatures, the colonies will remain suspended for extended periods. This is why it is not advisable to skip diapause; ants may enter diapause regardless but never come out of such a state or slow the colony down.

How can I determine when it's time for my ant colony to enter diapause?

You can observe their behaviour and look for signs of decreased activity, such as a reduction in foraging, caring for the brood, no egg laying, and other daily activities. Additionally, you can monitor changes in temperature and day length in their environment and compare it to the typical conditions under which diapause occurs for that species of ant. Ultimately, the decision to enter diapause is made by the colony, but you can help by providing the appropriate conditions for it. Usually, care sheets indicate the length and when to start diapause for each ant species.

How to Care for Ants During Diapause

If you're keeping ants as pets, you'll need to take special care of them and induce them into diapause. Here are some tips for ensuring that your ants make it through this period of dormancy:

ATTENTION: It is imperative that you do not leave pupae in a colony during diapause, as it can result in the death of the developing ant and increase the risk of mould growth.

IMPORTANT: Do NOT place your ants in the freezer, as this will kill them. Ants in the wild may be exposed to temperatures below freezing, but many species prepare for this by building up a natural antifreeze over several months. In captivity, ants do not have time to build up this antifreeze, so they must be kept above freezing temperatures during diapause.

What methods or options do I have?

Any method will involve using a source of cold, whether natural or human-made, to mimic the temperatures the ants would experience underground during winter:

Refrigeration; one of the most effective methods for diapause in captive ant colonies is the refrigerator method; it is also common to use a wine chiller or a mini fridge (thermoelectric cooler). Alternatively, a digital thermostat controller with a temperature probe can be paired with the appliance to achieve precise control. This method involves storing the ants in a unit that can be controlled to maintain a temperature of 5 to 9 celsius (42-48 F).
Placement in a cool room like an unheated basement, attic, or garage with temperatures averaging between 5-11°C (42-52º F), though there is a risk of fluctuation beyond this range.

The key to successfully inducing diapause in captive ant colonies is planning. To mimic the conditions the colony would experience in the wild, it is essential to understand the natural preparation process of ants for winter and adjust accordingly. In addition, some species may require different diapause conditions, so it is essential to research and understand the specific requirements of each species.

In the wild, ants naturally prepare for diapause by increasing their food intake to build up energy reserves, which will sustain them through the period of reduced activity during the colder months. They may also alter their nesting behavior, like sealing the nest entrances to conserve heat and moisture, or moving to deeper soil layers to escape the cold.

How to initiate diapause for an ant colony?

Prepare your colony: Feed them plenty of sugar and protein for a couple of weeks prior so they can build up reserves.
Ensure your ants have enough water and a clean test tube or nest. If they are running low on water, or have a dirty/mouldy nest, transfer them to a new setup before starting the diapause process.
If possible, gradually lower the temperature of the room or surrounding area 2-3 weeks before winter, and turn off heating cables or devices used to warm the ant farm setup. This gradual adjustment helps ants acclimate to the cooler temperatures, easing their transition into diapause.
Downsize the hardware if possible; for example, a large outworld won't be needed and can be replaced with a smaller foraging area. This also offers the opportunity to clean and refresh certain areas of the setup.
Ideally, place in a box or container that can allow for ventilation and insulation, for example, a cardboard box padded with towels or microfiber cloths; doing so allows to buffer/slow temperature changes and damp vibrations, applicable when coming out of diapause.
Place them in the cold area of your choice. When using refrigeration, start at a higher temperature and gradually bring it down daily ( 1 or 2º C), avoiding the lowest temperature immediately. Usually, the temperature should be maintained between 42-48 °F (5-9 °C) for temperate species and 60-65 °F (15-18 °C) for Mediterranean species. For example, if ants started at 25ºC and we aim for 6ºC, we can adjust every day 1º lower, which means we will take 19 days to reach the target temperature. It is ok to take 30 days or so to reach the target.

monitor the temperature of your ants during diapause

Caring for Ants Colony During Diapause:

Most ants do not require food during diapause but need moisture. Water your formicarium as usual, but you will notice that it takes longer for the nest to dry up in the winter compared to summer, so you do not have to water it as frequently. However, if your ants are in a refrigerator, you may need to water them more often, as the nest will dry up faster as some appliances dry up the air. If your ants are still in a test tube, a typical test tube setup with water should last them the whole winter.

Check on your colony at least once every three weeks if it is in a test tube to ensure that they still have water and have not experienced any floods or other issues. If your colony is in a nest, check on and refill their water as needed. Be observant without causing disturbances, especially if the ants are kept in a cooler or fridge where the air tends to be drier, and water the nest as needed to prevent dehydration.

How and when do I take my ants out of diapause?

After 3-5 months of diapause, it is time to take your ants out of diapause. Here are the steps to do so:

Remove from the refrigerator or cold area; ideally, power it down and let it sit so the temperature slowly rises before taking out the ants. Tempereature-controlled units can be programmed every few days with gradual increases in temperature until reaching room values, mimicking the natural rise in temperature until spring.
Warm up gradually; this is particularly important for ant colonies in test tubes, as a rapid temperature change can cause floods; having an insulated container can come in handy to make transitions softer, for example; do not remove a test tube from the fridge and place immediately on a heat cable.
Prevent floods; be proactive when coming out of diapause before warming up. Place the test tube at an angle, with the cotton above the water; this will help push less water into the cotton as air expands. If a flood does occur, you will need to move your ants into a new tube to prevent drowning; a tiny pipette can be handy to remove unwanted fluids in tight spaces.
Initially, provide them with more sugar to replenish their energy. Once you observe the ants becoming more active and foraging, gradually reintroduce protein into their diet. This will support the colony's recovery from diapause and prepare them for the active season ahead.

Taking your ants out of diapause with proper care and attention will allow them to return to their normal activities, ready to continue growing and thriving.

Prenolepis imparis (winter ants).

Prenolepis imparis, also known as "winter ants," have a unique foraging behaviour determined by their environment's temperature. They initiate ground surface activity, including foraging, when temperatures reach just above freezing and discontinue such activity when temperatures reach approximately 20°C. This enables the ants to gather food and resources while avoiding harsh weather conditions efficiently.

In addition to their winter foraging behaviour, Prenolepis imparis also have an estivation period during the hot months of the summer, which can range from 3 to 8 months in hotter and more humid climates like Florida. During this time, the colony shows almost no foraging activity and lives exclusively from the food stored by their "repletes." However, eggs are laid, and the brood is raised during this period, ensuring the colony's survival.

Prenolepis Imparis (winter ant queen) side view

Diapause in Ants: A Guide for Ant Keepers