Tetramorium immigrans (Pavement Ants)
This guide was written by Teej from the Ants and Ant-keeping Server
Introduction & Overview
As one of the most common ant species in the Eastern US and many other parts of North America, Tetramorium immigrans is a very popular species for beginner ant keepers. Colonies can reach over a thousand workers within one year! These ants are very easy to care for and pose few weaknesses to captivity.
Tetramorium immigrans' nuptial flights occur from early June-late July. They will fly in the mornings from 4am-7am, but queens can be found looking for a place to found later the same day as late as 5pm. If you miss a flight but would still like to find a queen, lifting rocks and tiles can often yield positive results.
This species is known to be pleometrophic which means multiple queens can found together, but as the first workers arrive, the queens will be killed until one dominant queen remains. Many keepers will put multiple queens together during founding so there will be more eggs from the start. Sometimes, these efforts will fail before workers even arrive and queens will either kill each other, or infertile queens will start eating the colony's brood. A pleometrophic founding method is not recommended.
A freshly captured queen from a nuptial flight will usually take anywhere from 3-14 days to lay her first batch of eggs. Without added heat, an egg will take approximately 6 weeks (1.5 months) to develop all the way to a worker. If you were to add heat through a heat cable, heat mat, etc. at 85F (29C) then you can expect an egg to develop to worker in approximately 4 weeks (1 month).
Tetramorium immigrans is well known for their willingness to eat nearly any food thrown their way. From my experience, and many others around the community, feeding a varied protein diet seems to increase egg production from the queen.
Some protein foods Tetramorium immigrans will accept are:
- Fruit flies
- Fish flakes
- Nearly any feeder insect
(Please note this species will eat nearly anything you offer including dog/cat food, their diet is not limited strictly to the items listed, but if a food is too moist they will bury it rather than eating it.)
Some sugary foods Tetramorium immigrans will accept are:
- Sugar water
- Protein jelly
- Organic fruits
- Queens are 6-7mm long
- Normally, queens have a dark brown or black colored body and antenna with reddish orange legs
- Tetramorium immigrans queens have 2 propodeal spines at the end of the mesosoma (thorax)
- Queens have 2 petiole nodes between the thorax and abdomen
- The mesosma (thorax) gets thinner as you progress down the ants body froom a birds eye view
- Well fed queens typically have 2 orange/yellow stripes at the end of the gaster (abdomen)
This species is commonly confused with Pheidole, Myrmica, and Aphaenogaster. Pheidole queens are usually smaller and have 3 visible ocelli on the top of their head. Myrmica queens are much thinner than Tetramorium and have a small, raised body, while Tetramorium immigrans queens have a more flat and thick body. Aphaenogaster queens will have a hunchback type presence with a highly elevated body, and a much larger mesosoma (thorax) than a Tetramorium queen. Aphaenogaster queens are also a bit larger than Tetramorium immigrans queens.
Tetramorium immigrans can found well in both test tube and petri dish setups. If your queen has not laid eggs 14+ days after capture, you may want to start questioning her fertility. Not all hope is lost if she has not laid within 14 days, but be careful. This species has a very low failure rate and will very often be raised to workers.
Feeding a queen a dab of honey just after being captured may be a good way to energize her if you're worried she is exhausted, other than that, I do not suggest you feed her while founding in order to avoid stressing her out. This species does not require any substrate to dig or a naturalistic setup to found properly. Many believe Tetramorium immgrans does not require to be entered into diapause (hibernation) as they have not seen any negative side effects.
This species is not polygynous and you should not expect multiple queens to live together peacefully after workers arrive. Sometimes new keepers will mess up and put multiple queens together expecting them to coexist only to be surprised when one queen remains.
Sand is probably the best substrate to use for this species as they are small and substrates of larger sizes they could choose to nest under/inside of.
Temperature: 85F (29C) in a gradient ideally
Humidity: High humidity preference
From my experience Tetramorium immigrans will move their eggs and larvae as close to moisture as possible. However, they seem to keep pupae slightly away from the more humid parts of their nest. Unlike humidity, they will move their pupae closer than their larvae and eggs to heated portions of the nest. I, and many other keepers, heavily recommend a temperature and humidity gradient for these ants.
Time to first workers: 6 weeks (1.5 months) unheated. 4 weeks (1 month) heated.
Tetramorium immigrans typically takes 6 weeks to raise from egg to worker while unheated. When heated, development will take approximately 4 weeks. Lone queens are pretty fearless and won't panic too much while being checked on as long as you avoid extreme vibrations and bright light.
These ants are extremely aggressive and will swarm their food, they are very active and entertaining to watch. Removing the cotton to a Tetramorium immigrans colony's test tube and placing them in a tub with a sandy substrate is a great way of giving them an outworld and easy place to feed. These ants will sometimes use their substrate in their nest to rest brood on. If feeding in a test tube becomes nearly impossible without escapees, I suggest you give them an outworld for easier feedings. Colonies of 1000 workers or less will usually send about 10%-25% of workers to forage outside of the tube. Young colonies should be fed protein 2-3 times a week and sugar at least twice every week. Although this protein schedule will keep the colony happy and healthy while maintaining a stable population, feeding protein once every 1-2 days will optimize their growth. Almost any feeder insect will be accepted along with artificial proteins like fish flakes and pellets. Sugars like honey and sugar water are readily accepted by younger colonies.
Some problems you may run into while keeping Tetramorium immigrans:
- Workers drowning in honey
- Food molding in tube/nest
- Not enough workers foraging
- A mild sting
When in a tubs and tubes setup, using a flat surface like a playing card or paper is very helpful when feeding. Sugar can be offered on wax paper. If you fear these ants escaping, take note that they sometimes struggle to climb glass and common barriers like PTFE and baby powder + alcohol solutions work very well. I suggest a thick barrier for Tetramorium immigrans as they can slowly tear away at the barrier over time, and with a thinner one they could breach it before you notice.
This species should be moved into a formicarium when their workers will cover at least 2/3 of the nest's size. These ants will thrive in almost any well made formicarium that can provide humidity, they will often do especially well with a humidity and heat gradient. The quantities Tetramorium immigrans should be fed in can be determined by worker behavior and colony size. Colonies ranging from 1-100 workers should be fed protein and honey once a week, while colonies 100-500 should be fed honey and protein twice a week. And colonies of 500+ workers should be fed honey and protein 5+ times a week in order to maintain steady growth.