Solenopsis Geminata, a Queen’s perspective

First of all, if you would like to access the reference papers that will be mentioned on this post, please click the link below.

And if you would like to see the video, please scroll down to the bottom of the post.

The Tropical Fire Ant (TFA), Solenopsis geminata (Fabricius) 1804, is native to South and Central America and has spread to many other parts of the world have become serious pests. 

They build conspicuous earthen mounds, which are aggressively defended by the painful stinging of often great numbers of workers. They have a high reproductive rate, a high population density, an efficient dispersal behaviour, and wide geographical distribution. 

These ants inhabit disturbed environments, often in areas of human habitat modification, and so, people are often forced to alter outdoor activities where fire ants are present. Fire ants can sting repeatedly. Symptoms of a fire ant sting include burning and itching. The ant injects venom containing an oily alkaloid called Solenopsin that is toxic to cells. It causes a white pustule to form in a day or two. Although the sting is not usually life threatening, they are easily infected and may leave permanent scars. This nuisance will generally lower the tolerance of their presence among humans.

So why would I or anybody want to keep Tropical Fire Ants?!

Well, first of all they are readily available, easy to start with and grow to very large numbers, making awesome and huge displays, the only real problems are containing them properly, maintenance and that awful sting, but truth being said, Geminata sting is way more forgiving than an Invicta sting.

23rd December 2019

2nd January 2020

So I decided to have a very large Tropical Fire Ant colony. Some of you may not know yet, but this year, the local Science Center is opening a biodiversity exhibition and I will display some colonies there, and I thought that having a giant fire ant colony in display would be incredible. 

So let’s put you up to date on how our 25 Queens are doing! As you can see they have been separated into 6 small AMAC nests. 5 nests with 4 queens each and 1 nest with 5 queens.

I already have a small colony starting as well 😀

As you may remember they were initially all together and seemed to be doing fine, but unfortunately they were attacked by dust mites which ate all their eggs. So I had to remove all the queens, inspected one by one for any unwanted mites, and then placed them in a communal nest for 24 hours with a humid cotton (to attract any remaining mite) and a honey water dish to replenish their reserves. 

After 24 hours, I separated them into those smaller nests, as I wanted to increase the chances of having a viable colony from all these queens. And after some 48ish hours, they started to lay eggs!!

From my last video about these Queens, I got some question asking if they wouldn’t kill each other and if they weren’t monogynous, well I got some really interesting information to share with you, hope you stick around because it’s going to be worth it.

The species of Solenopsis, were considered to be monogynous until Banks et al. (1973), and Glancey et al. (1973) observed polygyny in Solenopsis geminata (Fabricius) and Solenopsis invicta (Buren), respectively.

Polygyny, is the coexistence of two or more egg-laying queens in a single colony of a social insect, occurs in several subfamilies of ants (Wilson 1971)

According to Banks W.A, Plumley J.K. and Hicks D.M. 1973 Polygyny in a Colony of the Fire Ant Solenopsis geminata, “although the queens of some ant species have long been known to unite to found colonies (pleometrosis), only a few species have been observed to have multiple queens in a single well-established colony (polygyny). In March 1971 in north central Florida (Union County) while opening the nests of field colonies of S. geminata and S. invicta for study, we noted 2 highly physogastric dealate females in a single well-established nest of S. geminata. The 2 Q and ca. 50 worker ants from the nest were taken and returned to the Insects Affecting Man Laboratory at Gainesville, Fla., for study. Each female was placed with ca. 25 workers in a separate plexiglass ant nest. Egg production began in each nest within 72 hr after establishment, small larvae were apparent by 10 days, pupae by 18 days, and the 1st workers by 27 days. Both colonies continued to grow and after 90 days, each was composed of several thousand workers. The queen died in one colony after 114 days so the remaining workers were placed with the other colony and were accepted with little animosity. The results indicate that both the dealate females were fertile, and that mature colonies of S. geminata may contain more than one functional queen.”

Few years later, in 1976, Adams C.T, Banks W.A and Plumley J.K. , two of the same previous authors wrote, Polygyny in the Tropical Fire Ant, Solenopsis geminata with Notes on the Imported Fire Ant, Solenopsis invicta, an incredible article and experiment, reporting the observations of true polygyny in the Tropical Fire Ants, Solenopsis geminata. “Thirty one queens of the tropical fire ant solenopsis geminata were found in a single nest in the field… 14 of the 31 queens were established in individual 10cm circular plexiglass ant nets with circa 25 worker ants each. All colonies were maintained at a temperature of 27+- 2C. Queens started to produce eggs within 24 to 48 hours. At day 7 – each nest contained numerous larvae; at day 16 – worker larvae were present in all 14 nests; at day 25 – callow workers were present in all 14 nests. Oil soluble dyes of 7 colors were incorporated into the food of the ants of 14 individual colonies (2 colonies per color). The ants were permitted to feed ad lib for 7 days. Individual colors appeared in the eggs laid by queens feeding on their respective dyes. Colonies were recombined on the 17th day and the colors continued to appear in the eggs deposited in the large colony (for 2 days only) until trophallaxis blended the dyes to the point that they were indistinguishable, indicating a continued mutual contribution by each queen present in the composite colony. All laboratory colonies produced worker ants indicating that all queens had been inseminated. The eggs, larvae and pupae produced by the 14 queens were, at a later stage, tended mutually in a common nest by all of the 14 queens and their combined workers, an exmaple of true polygyny. […] Colony founding by groups of queens may be a prominent factor in the survival of new colonies of Solenopsis. Markin et al, found that when colonies were started by 3 queens nearly one third more of the colonies survived than when colonies were founded by a single queen. Our observations suggest that some mature colonies of Solenopsis may adopt newly mated queens after nuptial flights, this evidence is in direct contrast to the reports of numerous researchers who have seen workers of established colonies quickly kill many newly mated queens as they alright on the soil surface after the nuptial flight. Why worker ants sometimes kill the newly mated queens and apparently sometimes do not is uncertain.”

Once polygyny was verified and atested in Solenopsis geminata, then the next step was to understand in which situations it occurs, since in its native areas it forms primarily monogyne colonies, and what are the costs and benefits associated with the variation in queen number in fire ant colonies.

According to Vargo, E.L. 1993 Colony Reproductive Structure in a Polygyne Population of Solenopsis geminata (Hymenoptera: Formicidae) results, “Polygyne queens of S.geminata produce fewer eggs and far fewer sexual offspring than do queens in monogyne colonies, due to the suppression created by the higher number of queens. In S.invicta, this is caused by the higher levels of inhibitory queen pheromone resulting from the combined secretion of the queens. It is not known whether a similar influence occurs in S.geminata. Although the study reported considerable variability in fecundity among nestmates queens in polygyne colonies of S.geminata, there was no strong indication that egg laying was dominated by an individual or group of individuals.”

2 years later, in 1995, a new observation was documented, something that would bring a completely new perspective to the previous studies findings. 

Lets first clarify what are the existing reproductive strategies classifications that occur in ant species. Ants employ two primary strategies in establishing new colonies, the independent colony foundation (ICF) and the dependent colony foundation (DCF). 

ICF is characterized by new queens dispersing alone and need to raise their first generation of offspring without the help of nest mate workers. Examples of ICF include: solitary founding (claustral or semi-claustral); pleometrosis (the occurrence of several queens in a single nest of ants); and social parasitism.

DCF is characterized by existing established colonies, being divided into different groups that will then become independent from each other. These new groups will have to disperse terrestrially instead of aerially. The queen or queens, normally brachypterous queens, ergatoid queens or, gamergates, will be escorted by some of their nest mate workers to their new site location. They may or may not bring along some of the original nest brood. DCF includes a variety of dispersal methods, including: fission and budding.

Pleometrosis does not always equate to polygyny. Pleometrosis refers to colony formation by multiple queens of the same species, while polygyny refers to nests containing more than one reproductive queen. A species can operate pleometrosis during foundation and yet be a monogynous species. This is for most cases related to ICF founding strategies following pleometrosis principles, and generally, once the first workers emerge, only one queen will remain, while the others are evicted or killed.

McInnes D.A. and Tschinkel W.R. 1995 Queen Dimorphism and Reproductive Strategies in the Fire Ant Solenopsis geminata (Hymenoptera: Formicidae), “In this paper we present out observations on a queen dimorphism in the fire ant Solenopsis geminata. We believe this to be the first record of a non-parasitic ant which founds colonies dependently and yet does not undergo colony fission nor budding, and the first record of microgyny in a monogyne ant population. Alate trapping studies of a monogyne population of the fire ant Solenopsis geminata indicate that two sizes of gynes are produced. Macrogynes, which participate in late spring and summer mating flights, are larger, fattier, and more than twice as heavy as microgynes, which participate in fall mating flights. […]

[…] Behavioral evidence and rearing studies suggest that macrogynes found new colonies independently, whereas microgynes achieve colony queen status by infiltrating or being adopted by established colonies. Of the total number of female alates collected from the trapped colonies, 56% were microgynes. However, because of their smaller size and lower fat content, microgynes made up only one-third of the caloric investment in female alates. By measuring the thorax lengths of queens from wild mature colonies, we determined that at least 56% were macrogynes and 35% or more were microgynes. These results indicate that as a reproductive strategy, colony investment in microgyne production may have at least as high a payoff as investment in macrogyne production. […] We attempted to verify if existing colonies (with reigning queen present)  will adopt microgynes. […] Together, the apparent attraction of newly mated microgynes to existing nests and their lesser ability to rear brood claustrally (i.e., without foraging) suggest that microgynes are adapted to assume the role of matriarch after adoption by existing nests, rather than to initiate new colonies independently. Supportive evidence comes from the fat extraction results. […] Despite our failure in introducing microgynes, the microgyne adoption hypothesis cannot be discounted. […] In our opinion, S. geminata microgynes are unlikely to be successful unless they are adopted by orphaned colonies. This hypothesis best explains the results of our rearing studies and behavioral observations on S.geminata. Although our single trial with a newly mated microgyne proved unsuccessful, orphaned nests of S. geminata, in both the laboratory and the field, often accept replacement queens from other colonies.”

So how does polygyny and microgyny (with parasitism) relate to each other? Well, Glancey and Lofgren had reported in 1988 that a method by which polygynous colonies of S. invicta perpetuare themselves is via the adoption of newly-mated queens following their mating flight. This indicates that workers from polygynous colonies may accept alien queens, so explaining some of the previous results, if we assume the same occurence for Solenopsis geminata species.

Glancey and Lofgren 1988, Adoption of Newly-Mated Queens: A Mechanism for Proliferation and Perpeturation of Polygynous Red Imported Fire Ants, Solenopsis Invicta Buren, “The polygynous form of the red imported fire ant, Solenopsis invicta Buren was first reported from Mississippi in 1973; however, the source of the numerous fertile queens in polygynous colonies has remained an enigma. In 1987, 400 queens from a mating flight were marked with a durable paint and released in an area heavily populated with the polygynous form. None were recaptured after one week, but 9 months later, 4 clearly-marked queens were found in a nest 65 meters from their release point. This finding clearly points to adoption. About 5 weeks later, 37 of 107 fertile queens collected from 37 polygynous nests, were found to have partially histolyzed wing muscles and undeveloped ovaries. Mating flights had occurred a few days prior to the queen collections, thus it was apparent that these queens were newly adopted. This observation was verified following a second mating flight one week later. The results of our 3 studies clearly indicate that polygynous S. invicta can proliferate and perpetuate their colonies by queen adoption. However, we do not know the specific conditions which favor adoption, since it is obvious that not all queens are accepted.”

Unfortunately I couldn’t find any research that validates this theory in Solenopsis geminata, but I would say it’s not too far fetched to assume it as true, since all S.geminata posterior studies report so far very similar results as those done with S.invicta.

So it is commonly assumed that monogynous colonies are doomed after the death of the queen, but evidence indicates that colony takeover and adoption of unrelated queens in polygynous colonies are not a rare phenomena but it might actually occur quite frequently in many ant species.

Mortality rates of queens during solitary colony founding are usually high because of the limitation of suitable nest sites, adverse climatic conditions or predation. But by successfully, being adopted into an established colony or taking over an orphaned one, the young queen has considerably increased her chances to reproduce. Below we can find a list of some species found to contain unrelated matrilines inside their colonies. 

From Heinze and Keller 2000 Alternative Reproductive Strategies: a Queen Perspective in Ants

“The replacement of old queens by young, unrelated queens, in both polygynous and monogynous species, raises important questions for social insect researchers. How frequently do colonies recruit related versus unrelated queens? Are unrelated queens frequently able to enter and displace the breeding queen in monogynous colonies? If so, how do these queens circumvent the mechanisms of recognition that generally allow workers to effectively exclude non-nestmates? […] Finally, the finding that the breeding structure of ant colonies is more easily altered than had been thought previously, calls for an integration of both life history and kin-selection perspectives in the study of social evolution and kin conflict.”

So I hope you have enjoyed this combined article I put together. And how will this translate into my own Ant Keeping experiences?

Well, right now based on the presented information, I assume I have microgyne queens, based on the time of year I captured them (unfortunately I can’t take any measurements), another reason why I think it’s best to continue to keep them together and feed them, if it is true, then they probably wouldn’t be able to found by themselves separately. So let’s see how all this will turn out.

To end the article, I leave you with a question, wouldn’t it be totally awesome to test this theory with AntsCanada Fire Nation when it got orphaned?!

Thank you for reading, hope you enjoyed, and see you on the next one!


YouTube video on the same topic:

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