This article by Jerry Cates, Kavin Bizzell, Sylvia Tejeda, et al., first published on 4 November 2012, was revised last on 22 November 2012. © Bugsinthenews Vol. 13:11(01)
As mentioned in an earlier article (published on 27 June 2011) on little black ants, there once was a time when, in Texas, the pharaoh ant (Monomorium pharaonis Linn. 1758) was one of the most significant pests of human dwellings. Leland Howard, in his 1914 monograph on the insects, stated plainly that what he called the “little red ant” was “a pest of households.”
But its fame preceded the time of Leland Howard by more than a century, and probably many centuries before that. The species — named by Linnaeus in the 18th century for the plague-like manner in which it invades habitations, hospitals, nursing homes, and commercial kitchens (some believe the Master Taxonomist of Olde thought this ant represented one of the biblical plagues cited in Exodus ch. 8-13) — was even then one of the most vexatious pests known to man. When I first encountered this ant in Texas, in the late 1970’s it was still the ant scourge du jour, not only in Texas but throughout the United States. But that was about to change. By the early 1980’s, the red imported fire ant, or RIFA (Solenopsis invicta Buren 1972) had ascended the highest throne of ant infamy. The RIFA had spread steadily outward from the docks of Mobile, Alabama, where it first arrived in the U.S. from Brazil in the 1930’s. The destructive nature of its relentless advance, unchecked here by the natural predators that kept it under control in its native setting, was already legendary (though its northward progress appears to have been blocked by the winter frost line).
Still, among the problematic ants of the 1980’s and most of the 1990’s, the pharaoh ant remained an important a pest of homes and medical facilities. Its importance as a pest was bolstered by suspicions that it was capable of transmitting disease, via ordinary cross-contamination and other mechanisms, within hospitals and nursing homes. Though little in the way of scientific proof ever emerged to confirm that suspicion, the notion made enough sense to stand on its own. For that and a host of other reasons, tens of millions of dollars were invested by the pesticide industry in research programs, both internally and as research grants to the halls and labs of academia, to find effective control measures that could be employed by pest managers and homeowners alike.
I discuss briefly the history of the scramble for new pesticides to fight pharaoh ant infestations in the previous article on little black ants. That discussion is expanded upon in this article, below.
Of the various pesticides then (in the late 1980’s) under analysis for pharaoh ant control, one of the most promising was a rather non-exotic synthetic terpenoid — an isoprenoid derived initially from botanical sources, usually with a pleasant, somewhat floral fragrance and a well-established mode of action — known as methoprene (11-methoxy-3,7,11-trimethyl-2,4-dodecadienoic acid 1-methylethyl ester). Methoprene functions in arthropod biology as a juvenile growth hormone analog. When applied to the nymphs of developing larvae, particularly of insects that undergo complete metamorphosis (such as ants and a number of other social insects), development is permanently arrested before the adult stage is reached. Thus methoprene is capable of bringing the propagation of entire ant colonies to a halt.
The ZOËCON Corporation (now Wellmark International), which was founded in 1968 by a group of prominent scientists — among them Dr. Carl Djerassi, one of the developers of the first birth control pills for women — first registered methoprene for horn fly and mosquito control in 1975. Later, in 1980, the company registered the same molecule for flea control, and by the mid-1980’s, in a unique formulation (Pharaoh-Rid®) specifically targeting pharaoh ants.
That special formula was made necessary, by the way, because something (e.g., the emulsifiers and other inert ingredients in the various forms that methoprene was packaged in at the time) in the methoprene formula made it useless for pharaoh ant control. It worked well as an insect growth regulator, when applied directly to the target insects, but when ants — in particular, pharaoh ants — came into contact with food products containing traces of the emulsifiable methoprene formulation, they behaved so erratically thereafter that they seemed unable to return to their nests. I remember testing experimental baits I made in 1991 — from emulsifiable methoprene mixed with peanut butter and cinnamon bun paste — on pharaoh ants that were invading a nursing facility in Georgetown, Texas: the ants would palpate the paste with their antennae, then grasp a small quantity of the paste with their mandibles, and commence walking in slow circles, apparently so disoriented that they could not find the pheromone trail that led back to their main colony. After a few minutes the number of milling ants would grow, eventually reaching a critical level at which — from all indications — their antics had the effect of warning all the newly arriving ants not to approach the paste, lest the same calamity befall them. This caused the new arrivals to leave empty handed, presumably never to return. Hours later the paste would remain essentially as before, but surrounded by a small number of disoriented ants, all of whom walked aimlessly about in endless circles.
Experimental ant bait stations, modified by EntomoBiotics Inc. from rodent bait boxes,are today being used to deal with large pharaoh ant and other tramp ant colonies throughout Texas. These bait stations have their entry and exit openings closed off so rodents and other large insects and animals cannot get inside. Holes are drilled in the sides to allow small organisms, primarily ants, to enter and exit with ease. Inside are placed bait formulations made with ordinary food items such as pureed bacon and bacon grease, pureed hot-dog wieners, and bakery goods such as bread and cinnamon buns (a favorite with most ants), impregnated with measured quantities of insect growth regulators and/or toxicant materials labeled and approved for ant control purposes. A glue trap is also installed to capture a few of the ants that forage inside the box for later analysis under the microscope. When the baits are examined later, and the kind of food the ants prefer to eat becomes clear, that information is used to influence the mix of baits in the future. The bait stations are tamper resistant, and are attached to concrete block foundations, which make them difficult for animals to relocate and/or vandalize.
That problem was fixed with Pharaoh-Rid®. Dyed bright purple, the special Pharaoh-Rid® formula was sold in small syringes that were added to peanut butter, cinnamon bun, and pureed liver pastes made up by the pest manager. The final product, which had a reddish cast that “proved” it contained the suitable formulation of methoprene, was then packed into plastic drinking straws. The packed straws were then cut into one-inch sections, and later distributed in cryptic places where pharaoh ants were being observed. Over time, the pharaoh ant workers would carry enough of the bait paste back to the colony to sterilize all the queens and bring brood development to a halt, at which time the colony would cease to exist. And it worked, albeit slowly. As long as the pest managers involved did their work of mixing fresh batches of paste, adding the right amount of Pharaoh-Rid® to it, packing the mixture into plastic drinking straws, then cutting the straws into small sections and distributing them in the foraging area of the targeted pharaoh ant colony, a pest management firm could guarantee complete control of even the largest pharaoh ant colony in as few as six months.
For example, in the early 1990’s in downtown Waco, Texas, I began treating the twelve-story Regis St. Elizabeth Center. That facility had been infested with pharaoh ants for as long as anyone could remember (at least fifty years, according to one administrator) and though everything under the sun had been tried in the past, nothing had worked. I noticed that each floor had a number of easily opened access panels to the wall interiors, and this allowed me to place baits in every wall void of the building. I replenished those placements with fresh bait every month until, five months later, all pharaoh ant activity had ceased. Eight years later (the last time I checked) Regis St. Elizabeth remained free of pharaoh ants, even though no additional bait was placed after the first five months of treatment.
But all was not entirely rosy with the Pharaoh-Rid® program. The tedium involved in making and putting out the Pharaoh-Rid® infused baits was more than most pest managers were willing to handle. Worse, their customers balked at the expense. The high cost of the Pharaoh-Rid® syringes was only the beginning; after tacking on the labor costs associated with making and placing the bait straws, a typical pharaoh ant treatment program cost, at even a small residential home, $200.00 to start, and often rose to three to four times that amount when, months later, all pharaoh ant activity finally ceased. It was a hard sell, in a highly competitive marketplace. As a result, some pest managers were forced by the pressures of competition to absorb some or all of the costs of pharaoh ant management as part of their standard treatment programs. It should also be mentioned that not all eradication programs worked as well as the one I performed at Regis St. Elizabeth in Waco. When multiple colonies exist within the environment surrounding the target site, those colonies eventually impinge on the target to fill the void left by an eradicated colony. It may take months, or years, for that to occur; but if it occurs in a matter of months (as often happens in a residential neighborhood) the client will wonder if you really wiped the old colony out or if, alternatively, you merely suppressed it for a while. The hapless pest manager in such a situation is left footing the bill for remedial treatments of new colonies until the term of the guarantee runs its course, and sometimes that term can be quite lengthy…
Naturally, the push was on to find less expensive ways to bring pharaoh ant infestations to a halt. One such way was to ignore the budding behavior of pharaoh ant colonies and perform wholesale baiting with toxicant baits, on the theory that, by using a slow-acting toxicant that worker ants could carry back to the queen and larvae, distributing it far and wide before the toxic effects were evident, you would succeed in wiping out the colony before it could bud. It was a novel theory, and, in the final analysis, it worked as well as Pharaoh-Rid® and at a much lower cost. Soon a number of pesticide manufacturers were testing and marketing carbohydrate-and-protein-based ant baits infused with various slow-acting toxicants and insect growth regulators.
A bewildering array of novel, mostly exotic, pesticide molecules arrived on the scene during this same period, making it difficult for practitioners in the field to keep abreast of modern technology. Some amongst us (myself included), in the midst of the perplexity that so many “advances” produced, questioned aloud whether we should be considered beneficiaries or victims of this flurry of progress.
Answers, for those who sought them, were not long in coming.
A carbamate growth regulator with the chemical name fenoxycarb — ethyl N- [2- (4-phenoxyphenoxy) ethyl] carbamate — was marketed extensively in the late 1980’s as a somewhat exotic substitute for methoprene and its close cousin, hydroprene; this novel molecule, we were told, had an excellent toxicity profile, touted to be “similar to that of common table salt,” making it as safe around humans and pets as terpenoids like methoprene and hydroprene. Plus, unlike these terpenoids, fenoxycarb was effective against all insects, while methoprene was only effective against those with complete metamorphosis, and and hydroprene only worked with insects with incomplete metamorphosis. Those like me who got excited about low-toxicity products tried fenoxycarb out right away. We liked it’s apparent effectiveness, and worked it into our arthropod management protocols. When it appeared to work at least as well as methoprene and hydroprene, it made sense to switch between these IGRs on a regular basis, as an aid to lessening the risk of creating resistant pest strains.
Several years later, however, the EPA announced their latest toxicological findings. Fenoxycarb, far from being “as safe as table salt,” was now considered a class-B2-carcinogen…
This was a bitter pill to swallow, especially for those who had taken the manufacturer on its word and applied fenoxycarb sprays with careless abandon. In those days, “careless abandon” was very descriptive, as it was still common for the more macho pest managers to mix their pesticides in buckets with ungloved hands (in those days, disposable gloves were expensive and not in vogue), particularly if the tox profile for the product had been touted as unusually safe. Worse, similar examples soon surfaced, reminding the more observant, and usually less macho/somewhat skittish, practitioner (such as I) that unheralded risks sometimes attended the use of “new and safe” chemicals that came into the pesticide marketplace. It bears pointing out that few of these cases could have been predicted in advance just by examining the toxicological profiles on file, and that access to those files was not as easy as doing an Internet search (for all practical purposes, the Internet was not available to the average pest manager of the time). Even today, the true meaning of those profiles often escapes honest attempts at quantification. Controversies, swirling about every negative finding, were enough to fill a good-sized book, placing the practicing pest manager squarely on the horns of a dilemma.
One more example in particular bears elucidation. The fluoridated organic compound commonly known as sulfluramid — N-ethyl-1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8 -heptadecafluoro -1 -octanesulfonamide — was and still is (until 2014 or 2016, according to various sources) the active ingredient in a variety of ant and termite baits that were first marketed in the 1980’s. Again, sulfluramid, though an exotic molecule, was initially promoted for having an unusually safe toxicity profile.
Years later the EPA judged this highly persistent compound to be potentially teterogenic, and toxic to developing human fetuses, human reproductive organs, and human kidneys…
Ingestion of the contents of a single ant bait packet containing sulfluramid by a human child has, according to some investigators, the potential of causing permanent damage to the child’s reproductive organs. Absorption of sulfluramid through the skin of adult humans who come into direct contact with the active ingredient has the potential of producing (1) injury to developing fetuses carried by pregnant women, (2) damage to the adult’s reproductive organs, and (3) damage to the adult’s renal (urinary) organs. Again, the studies that led to such judgments are controversial and subject to various interpretations. However, the EPA considered them significant enough to require phasing out all sulfluramid-based products, but — paradoxically — not significant enough to force a halt to the manufacture and sale of those products before existing stockpiles of baits and technical grade materials are exhausted.
My point in discussing these conundrums here is to demonstrate the range and depth of the difficulties faced — then and now — by those in the pest management community who must decide the best way to deal with pharaoh ant and similar types of arthropod infestations. One has to weigh the potential risks posed by the remedy against the potential risks represented by the target pest, and as the above should make clear neither risk is so adequately defined as to enable even a careful judge to view the scales with absolute clarity of vision. Ultimately the question distills down to which way one should err… A. On behalf of a new and exotic molecule’s proponent, and their promises of greater profits? Or B. With humanity’s and one’s own health concerns, avoiding the newly announced exotics until their safety is firmly established, while exhausting every known, firmly safe measure at one’s disposal? For me the answer was clear and unequivocal.
Suffice it to say that, over a period of about fifteen years, enough excellent, good, and fair remedies reached the market to make a solid dent in the pharaoh ant populations throughout the United States. As a result that species, though not completely decimated, has today lost much of its “ferocity” as a pest of habitations and medical facilities.
The pharaoh ant has a reputation for producing polygyne colonies (with more than one queen) and for “budding” when the population of a given colony dropped precipitously low (as may occur when pesticides wipe out large numbers of the colony’s worker ants).
Budding is an adaptational defense to predation that leads the colony’s brood workers to split the nest into several satellite “buds” that — along with at least one queen — march off in different directions to found new colonies elsewhere. When fast-acting pesticides are used against ant colonies that are prone to budding, the end result does not reduce the scope of the original infestation, but rather enlarges it. When all or most of the workers that have gone out to find food and bring it back to the colony suddenly disappear, never to return, the ant colony recognizes that a catastrophe has occurred, and reacts in a predictable manner. Overnight single colonies fracture into a multitude of budded colonies that move out in all directions, away from the original nest. These budded colonies, though initially small, speedily become as large as, or even larger than, the original colony they spring from.
How habitat affects pest management issues:
Fig. 201 shows the expanse of dense jasmine ground cover that comprises much of the perimeter this medical facility, located in Central Texas. Such landscaping provides visitors with a visible ambiance of unusual beauty, but at a high price. Besides serving as cryptic habitat for rodents and other animals, it encourages aphids to infest its tender new growth each spring, and they — in turn — not only attract tramp ants such as pharaoh and little black ants to the area, but offer them a temperature and humidity stabilized environment in which to thrive during the late spring/early summer and late summer/early fall seasons. Absent remedial pest management mitigation, ant colonies that develop outside in these periods will later move into the medical facility’s interior during the unfavorable conditions that prevail during the mid-summer and mid-winter seasons.
Fig. 202 shows the climax forest of mature oaks and conifers, with a thick layer of dense shrubs, vines, and herbaceous undergrowth below, that borders another medical facility in Southeast Texas. Here a vibrant botanical potpourri offers animals of every variety, including practically every species of ant native or introduced to the area, a temperature and humidity stabilized environment in which to thrive throughout every season of the year. Absent remedial pest management mitigation, ant colonies infesting this wilderness are free to forage within the grounds of this medical facility at will, and can be expected to invade the interior of the facility searching for food whenever they wish to do so (indeed, the medical facility involved here is presently the subject of an on-going invasion of rasberry crazy ants).
In both of the above situations, remedial pest management mitigation is imperative, not only to deal with incipient ant infestations in the grounds and surrounding wilderness areas, but with those that would likely invade the facility interiors as well. Such procedures, however, must emphasize the use of non-toxic products and reduced-risk methods, in keeping with the fact that these sites are, after all, medical in nature, where the introduction of toxicant products is inimical to the overweening objective of the institution. The remedial programs we are developing are multidirectional, and include mechanical habitat modification of the landscaping at each site as well as the installation of specialized ant bait stations in the grounds to reduce the numbers of foraging ants and thus reduce the pressure of potential invasions of the building interiors.
The pharaoh ant is also famous for producing polygyne colonies capable of living entirely within man-made structures. Such colonies were thought, at one time, to rarely forage outdoors, but that notion has been disproved in most parts of Texas and similar sub-tropical and mildly temperate regions. When conditions are right, pharaoh ants will forage out-of-doors as much as indoors. On the other hand, during the hottest part of the summertime, and the colder parts of the winter months, they forage indoors almost exclusively. What this means is that, twice a year, i.e. (1) during late spring and early summer, and (2) late summer and early fall, pharaoh ant colonies forage freely outdoors throughout most of Texas, but tend to confine their foraging activities to protected, temperature-and-humidity-stabilized environments during the winter and summer months.
Let’s discuss briefly what that means.
There are two primary sources of temperature-and-humidity-stabilized environments in most locales. Primary among these is the natural stabilization provided by thick climax forest replete with an impenetrable lower level of shrubs, vines, and native plants. Those conditions are often mimicked, intentionally, by homeowners and caretakers of commercial structures who envelope their buildings in dense shrubbery underlain with expanses of impenetrable ground cover such as jasmine and similar botanicals.
Secondarily, homes and commercial structures that provide climate control in the form of air-conditioning in the summertime — and furnace heating in the winter — provide the kind of temperature-and-humidity stability that is ideal for pharaoh ant colonies to thrive. If we were to map the environment within a given locale to show the areas where temperature-and-humidity-stabilization is provided, either by climate controlled structures or by forests and their associated brushlands, we’d see a series of islands within which pharaoh ants and similar insects would be expected to thrive throughout the year, separated by less ideal environments within which those organisms would be expected to venture forth during late spring, early summer and late summer, early fall. Ideally, those islands would be separated by enough distance to reduce the likelihood that colonies in one would wind up foraging in the surrounding islands. The reasons why are straight-forward: if you succeed in eradicating the pharaoh ant colonies in one island (say, for example, a nursing facility that you have control over), but not in an island nearby (say, for example, a forested area, or a hospital next door, that you do not have control over), any pharaoh ant colonies in those nearby islands that manage to forage in your island during the temperate periods of the year will find the setting ideal to set up shop in, simply because — absent the competition that an existing infestation of pharaoh or even another species of invasive ant would provide — they would enjoy free rein to build new colonies with abandon. Then, voila! You have a new pharaoh ant infestation to deal with.
Case in point: the little black ant colony described in my article of 27 June 2011 was infesting a medical facility in Round Rock, Texas. That facility is, first, surrounded by lush landscaping that includes a broad expanse of thick jasmine ground cover shaded by a number of mature oak trees, creating an outside environment ideal for pharaoh ants to thrive in during the most temperate months of the year, and to survive in throughout the year. Beyond that, the facility is bordered by a number of surgical, clinical, and diagnostic facilities, and though each of is surrounded by equally lush landscaping, not one of the neighboring structures was included in the treatment regimen conducted at the target site. It was no surprise, then, that once my work at this facility, in 2011, succeeded in eliminating the little black ant colony there, it was not long before pharaoh ants began to show up, presumably as a result of foraging soirees originating in neighboring colonies that were presently infesting one or more of the nearby structures. Though serious efforts have been carried out to eliminate them, they continue to rebound, primarily during the temperate intervals separating the summer and winter seasons. They come from the exterior landscaping, which most likely is constantly replenished by budded colonies emanating from the neighboring structures. This points up the importance of including — if at all possible — all of the nearby structures in future ant control programs here.
EntomoBiotics Inc. is currently studying this and a number of other pharaoh ant infestations in Round Rock, Texas, as well as in several other locations throughout Texas. Unique protocols, using experimental outdoor bait stations, non-toxic habitat modifiers, and insect growth regulators (IGRs) are being developed in the process, and will be tested in each of these locations to determine the best way to entirely resolve their infestations without exposing humans or their pets to pesticide toxicants in the process. The most promising approach appears to be a combination of habitat modification techniques, involving mechanical habitat modifications outdoors that reduce the foraging zones these ants can exploit during the temperate months when these ants move from one structure to another.
This posting is a work in progress, and will be fleshed out as time permits. Details of the pharaoh ant’s anatomical characters, and the exhaustive measures we are taking to deal with its infestations — focusing on the safest products presently on the market — will soon be added.
A detailed anatomical analysis of this species is in preparation.
- Kingdom Animalia (ahn-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus [23 May 1707 – 10 January 1778], using the Latin word animal = “a living being,” from the Latin word anima = “vital breath”, to refer to multicellular, eukaryotic organisms whose body plans become fixed during development, some of which undergo additional processes of metamorphosis later in their lives; most of which are motile, and thus exhibit spontaneous and independent movements; and all of whom are heterotrophs that feed by ingesting other organisms or their products;
- Phylum Arthropoda (ahr-THROPP-uh-duh) — first described in 1829 by the French zoologist Pierre André Latreille [November 20, 1762 – February 6, 1833], using the two Greek roots αρθρον (AR-thrawn) = jointed + ποδ (pawd) = foot, in an obvious reference to animals with jointed feet, but in the more narrow context of the invertebrates, which have segmented bodies as well as jointed appendages;
- Class Insecta (Linnaeus, 1758) — named using the Latin word insectum, a calque of the Greek word ἔντομον ( EN-toh-mawn) = “(that which is) cut into sections”; comprised of arthropods with chitinous external (exo-) skeletons, a three part body composed of a distinct head, thorax, and abdomen, the midmost part having three pairs of jointed legs, and the foremost part having a pair of compound eyes and antennae;
- Order Hymenoptera (hye-muhn-OPP-turr-uh) — first described in 1758 by the Swedish taxonomist Carl Linnaeus (1707 – 1778), who combined the Greek words ὑμήν (pron. humēn) = “membrane” + πτερόν (TARE-awn) = “wing”, thus ὑμενόπτερος (hew-men-OPP-tehr-ose) = “membrane-winged” to refer to insects with membranous wings, specifically the sawflies, wasps, bees, and ants; this is one of the largest orders of insects, and includes over 130,000 species;
- Family Formicidae (fohr-MISS-uh-dee) — first described in 1809 by the French zoologist Pierre André Latreille (1762 – 1833), from the Latin formica = “ant” to refer to hymenopteran insects that have elbowed antennae and a narrow waist that separates the thorax from the abdomen with a node-like petiole; at present, 20 distinct subfamilies of ants are recognized:
- Subfamily Aenictogitoninae: a subfamily comprising a single genus, Aenictogiton, with seven known species of rarely collected ants found in Central Africa with morphological and phylogenetic affinities to the army ant genus Dorylus; only males have been collected, and nothing is known about their workers, queens or behavior;
- Subfamily Agroecomyrmecinae: characterized by the following derived traits (see Bolton 2003): mandibular masticatory margins oppose at full closure but do not overlap; eye at extreme posterior apex of deep antennal scrobe; antennal sockets and frontal lobes strongly migrated laterally, far apart and close to lateral margins of head; abdominal segment IV with complete tergosternal fusion; sternite of abdominal segment IV reduced, tergite much larger than sternite and strongly vaulted;
- Subfamily Amblyoponinae (including the subfamily Apomyrminae): mostly specialized subterranean predators, comprised of a single genus of two species native to California; characterized by the following traits (see Bolton 2003): workers of this ant subfamily — which was formerly considered a tribe within the subfamily Ponerinae — exhibit the following characters: eyes small or absent, if present situated behind the mid-length of side of head; anterior margin of clypeus with specialized dentiform setae; the promesonotal suture is flexible; the petiole is broadly attached to abdominal segment 3 and is absent a distinct posterior face; the postpetiole is absent; a sting is present and is well developed.
- Subfamily Aneuretinae: this subfamily is comprised of a single extant tribe containing a single extant genus and a single extant species (several extinct tribes, genera, and species have also been described), namely the Sri Lankan relict ant (Aneuretus simoni); this is one of the few ant species considered endangered;
- Subfamily Cerapachyinae: a subfamily of 5 genera and 217 recognized species, distributed throughout the tropics; they possess spines on the pygidium; their antennae are short and thick; and they lack dorsal thoracic structures; they prey on other ant species;
- Subfamily Dolichoderinae: presently not divided into tribes, but comprised of 24 genera, including the Argentine ant (Linepithema humile), the erratic ant (Tapinoma erraticum), the odorous house ant (Tapinoma sessile), and cone ants in the genus Dorymyrmex; these ants are distinguished by having a single petiole, absent a post-petiole, and lacking a sting but possessing an apical slit-like orifice at the posterior abdomen instead of the round acidopore encircled by hairs typical of the Formicinae subfamily;
- Subfamily Ecitoninae (incl. “Dorylinae” and “Aenictinae”): New World and Old World army ants; in the New World, these ants are found in the tribes Cheliomyrmecini (containing the single genus Cheliomyrmex) and Ecitonini (containing the four genera Neivamyrmex, Nomamyrmex, Labidus, and Eciton); the genus Neivamyrmex — the largest of all army ant genera — contains more than 120 species, all native to the United States; the predominant species of the genus Eciton, E. burchellii, has been given the common name “army ant” and is considered the archetypal species; Old World army ants are usually divided into two tribes, Aenictini and Dorylini, but are often treated as a single tribe, Dorylini, alone; each contains a single genus; the genus Aenictus contains over 100 species, and the genus Doryus contains the aggressive “driver ants”, of which 70 species are known;
- Subfamily Ectatomminae: In North America a single genus, Gnamptogenys, is represented; that genus is not native to North America but has been introduced;
- Subfamily Formicinae: (fohr-mih-SEE-nee) — first described in 1836 by the French entomologist Amédée Louis Michel le Peletier, comte de Saint-Fargeau (1770 – 1845), usu. referred to as Lepeletier, from the Latin formica = “ant” to refer to a subfamily of ants whose evolutionary development is not as robust as most other subfamilies, e.g., they generally retain such primitive features as pupal cocoons, ocelli in workers, and a lesser tendency toward reduced palpal or antennal segmentation; all formicines have reduced stings and enlarged venom reservoirs, with a venom gland that is uniquely specialized to produce formic acid, and a one-segmented petiole having the form of a vertical scale;;
- Subfamily Heteroponerinae:
- Subfamily Leptanillinae: comprised of two tribes, the Anomalomyrmini (two genera, seven species) and Leptanillini (three genera, 41 species); within the tribe Leptanillini the larva provide their hemolymph as food to the queen through specialized processes on their prothorax and third abdominal segment; this behavior resembles that of the unrelated Adetomyrma, also called Dracula ants, which actually pierce their larvae to get at the body fluids; ants in the genera Leptanilla and Phaulomyrma are minute, yellow, blind, and subterranean;
- Subfamily Leptanilloidinae: 1 tribe, 3 genera, 15 species;
- Subfamily Martialinae: 1 genus containing a single species, Martialis heureka, discovered in 2000 from the Amazon rainforest near Manaus, Brazil, and placed as the sole member of a new subfamily (Martialinae); the generic name, which means “from Mars,” refers to its unusual “out-of-this-world” morphology; the species epithet heureka honors the surprise that accompanied its discovery; it is the oldest known extant species of ants;
- Subfamily Myrmeciinae (incl. “Nothomyrmeciinae”): once distributed worldwide but now restricted to Australia and New Caledonia; one of several ant subfamilies which possess gamergates, i.e., female worker ants which are able to mate and reproduce, thus sustaining the colony after the loss of the queen; formerly composed of a single genus, Myrmecia, but revised (Ward & Brady 2003) to include two tribes and four genera; three additional genera, one form genus, and nine species were later described (Archibald, Cover and Moreau 2006) from the Early Eocene of Denmark, Canada, and Washington;
- Subfamily Myrmicinae: approximately 130 genera in 23 tribes, and 10 additional genera not assigned to specific tribes, all cosmopolitan; the pupae lack cocoons; some species retain a functional sting; the petioles have two nodes; nests are permanent, in soil, rotting wood, under stones or in trees; the subfamily includes leaf cutters (tribe Attini), acrobat (tribe Crematogasterini), harvester (tribe Myrmicini), big-headed (tribe Pheidolini), and fire (tribe Solenopsidini) ants;
- Subfamily Paraponerinae: comprised of a single genus, Paraponera, containing a single species (Paraponera clavata), known as the lesser giant hunting ant, the conga ant, or the bullet ant (so named for its powerful sting); this ant inhabits lowland rainforest, from Nicaragua and eastern Honduras, and south to Paraguay; the ant is called “hormiga veinticuatro” by locals to refer to the 24 hours of pain following each sting;
- Subfamily Ponerinae: about 1,600 species in 28 extant genera, including Dinoponera gigantea, which is one of the largest species of ant found in the world; distinguished from other formicine subfamilies by their constricted abdomens;
- Subfamily Proceratiinae: similar to Ponerinae but the promesonotal suture is fused and the frontal lobes, elevated rather than transverse, are frequently reduced; antennal sockets are exposed in frontal view; in most species abdominal tergite 4 is much enlarged and vaulted, while abdominal sternite 4 is reduced; these are specialized predatory ants that are represented in California by a single species;
- Subfamily Pseudomyrmecinae: three genera of slender, wasp-like ants that forage alone and readily sting when molested;
- Subfamily Myrmicinae (murr-mih-SEE-nee) — approximately 130 genera in 23 tribes, and 10 additional genera not assigned to specific tribes, all cosmopolitan; the pupae lack cocoons; some species retain a functional sting; the petioles have two nodes; nests are permanent, in soil, rotting wood, under stones or in trees; the subfamily includes leaf cutters (tribe Attini), acrobat (tribe Crematogasterini), harvester (tribe Myrmicini), big-headed (tribe Pheidolini), and fire (tribe Solenopsidini) ants;
- Tribe Solenopsidini (soh-luhn-opp-suh-DEE-nee);
- Genus Monomorium (mohn-oh-MOHR-ee-uhm) — first described in 1855 by the Austrian entomologist Gustav Mayr (1830-1908), possibly using the Greek roots μονος (MOHN-os) = single + μορφη (MOHR-fee) = shape, form, in conjunction with the Greek diminutive suffix -ιυμ (ee-uhm) = denoting the quality or nature of, to refer to the fact that most ants in this genus, contrary to many others in the tribe Solenopsidini, are monomorphic (though some are decidedly polymorphic);
- Species pharaonis (fay-ROH-niss) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus [23 May 1707 – 10 January 1778], applying the Latinized form of the title of Pharaoh, in reference to the plague-like way these ants forage in household kitchens, bedrooms, and other places of human habitation.
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- Meyers, Jason M. 2008. Identification, Distribution, and Control of an Invasive Pest Ant, Paratrechina sp. (Hymenoptera: Formicidae) in Texas. Texas A&M University
- Pearcy, Morgan, Michael A. D. Goodisman, & Laurent Keller. 2010. Sib Mating without Inbreeding in the Longhorn Crazy Ant. Proc. R. Soc. B 7 September 2011 vol. 278 no. 1718 2677-2681.
- Stewart, Amy. 2011. Wicked Bugs: The Louse That Conquered Napoleon’s Army & Other Diabolical Insects. Algonquin Books of Chapel Hill.
- Taber, Stephen Welton. 1998. The World of the Harvester Ants (W. L. Moody Jr. Natural History Series). Texas A&M Press.
- Wetterer, James K. 2008. The Worldwide Spread of the Longhorn Crazy Ant, Paratrechina longicornis (Hymenoptera: Formicidae). Myrmecological News 11:137-149.
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