This article by Jerry Cates and Ramon Alaniz, first published on 22 November 2012, was last revised on 23 November 2012. © Bugsinthenews Vol. 13:11(04).
One of my clients in the city of Victoria, Texas, reported seeing tiny black “sugar ants” in certain locations several months in a row, yet not a single ant was present whenever I was on site. That, of course, is the way Murphy’s Law works. So, by way of contravening the nefarious effects of said Law, I gave the on-site maintenance director, Ramon Alaniz, some specimen vials so he could snatch up a few of these critters next time they appeared. My faith he’d come through on this was amply rewarded. On my next visit he handed over several vials of ants.
I ask a lot of the directors of the maintenance, nursing, dietary, and housekeeping departments at the sites I serve. At first my requests for help seem above and beyond the call of duty. Later they understand how collecting specimens of insects and spiders helps to determine the exact kinds of critters that are dropping by. This lessens speculation and guesswork, and enables me to put together a comprehensive, effective remediation program to deal with the pest problems that freak them out. For all the help these healthcare professionals provide, I offer my grateful thanks…
Under the microscope it was clear these were longhorn crazy ants (Paratrechina longicornis). For one thing, their legs were unusually long, and for another their antennae — conspicuously projecting above and in front of the head — were about as long as their bodies, whereas with most ants the antennae are not much longer than twice the length of their heads.
Their long legs make these ants unusually quick and somewhat erratic (i.e., crazy-like) in their movements. It was that observation that led the Russian entomologist Victor Motschulsky, way back in 1863, to craft the name “Paratrechina” for the genus this ant belongs to. By this name Motschulsky characterized the ants that genus embraced as (I’m paraphrasing) “fast, jerky-movers.” Some 61 years earlier, in 1802, their elongated antennae had inspired the French zoologist Pierre André Latrielle to craft for them the species name of “longicornis,” which is a contrived Latin word meaning “longhorn(ed).” I added the parenthetical -ed in deference to my fellow Texans who naturally think of animals with long horns as being “longhorned,” but for those of you not similarly disabled linguistically, the shortened version will do nicely.
Longhorn crazy ants are exotic “tramp” ants that have, over the long and storied history of man’s expeditious travels across the globe, managed to come along for the ride. But they did much more than hitchhike those terrestrial and marine routes: they also became inveterate settlers wherever they wound up. Because this species thrives in disturbed and artificial environments, including ships at sea and human habitations (Wetterer, 2008), and are apparently uniquely capable of mating with their siblings without suffering any negative effects of inbreeding — a process described as a double clone by its discoverers (Pearcy, et al., 2010) — the transplanted colonies tend to flourish in their new locations. These stratagems, in combination, enabled the species to bloom wherever they are planted, throughout the world. In fact, the species is so widespread that there are precious few places where it is not recognized as a pest.
Ask, for example, anyone who has been associated with that snake-bitten project known as BioSphere 2 (named the second because the Earth, itself, is considered BioSphere 1). BioSphere 2’s 3.14 acre structure, an Earth systems science research facility that Columbia University ran from 1995 to 2003, and that the University of Arizona operated from 2007 onward, and has owned outright since 2011, serves as a center for research, outreach, teaching and lifelong learning about the Earth, its living systems, and its place in the universe. It was originally built — after breaking ground in 1984, and reaching a shaky completion in 1991 — as a closed artificial ecological system designed to explore the complex web of interactions within earth’s recognized life systems.
Early on in BioSphere 2’s history a host of problems crept in, many having to do with the personalities of the humans managing and running the project. One significant non-human problem was an invasion of longhorn crazy ants. The ants, though starting out as a mere inconvenience, soon exerted an overwhelming effect upon the project. The problem? They quickly killed off many, if not most, of the other insects inside the BioSphere 2 structure, despite the fact that they don’t bite or sting humans or other large animals. Not too surprising, the cockroaches — widely believed capable of transcending any ecological catastrophe — managed to survive the crazy ant’s onslaught, as also did the katydids, a phytopathogenic nematode not found anywhere else in Arizona, and the common morning glory of the Convolvulaceae family, an invasive weed that has few natural enemies but that thrives under a wide variety of ecological conditions.
But back to my client in Victoria. Here the longhorn crazy ant is showing up in rooms where humans live, eat, and sleep. They are so small they manage to squeeze their way into the tightest cracks and crevices to get to food thought safely secured in plastic containers. Fortunately, as previously mentioned and in keeping with the behavior of their close cousin the Rasberry crazy ant, they do not sting or bite, so their incursions do not represent an imminent hazard to health and safety. But their presence is annoying, to say the least, and strenuous steps are being undertaken to deal with them at this site.
As with all our pest management operations, a comprehensive approach is underway. Emphasis is on non-toxic and least-toxic methodologies, including the employment of habitat modification techniques designed to create and maintain an environment that does not nurture or attract these ants. Insect growth regulators are also being distributed throughout the client’s site in the form of baits that contaminate the ants that feed on them, and that prevent reproduction of the colony.
More to come…
The longhorn crazy ant is a member of the Formicidae family, and the subfamily Formicinae, of insects (the order Insecta).
General Anatomy: These ants present with anatomical characters consistent with workers in the subfamily Formicinae (from Bolten, 1994), and the genus Paratrechina. For more information on these taxonomical units, see the section, below, on taxonomy.
Anatomical Characters of ants in the subfamily Formicinae (adapted from Bolten, 1994):
- The clypeus is broad, from front to back, so that the antennal sockets are well behind the anterior margin of the head (figs. 104-105, 108). The median portion of the clypeus does not extend backward between the frontal carinae, but a postclypeal frontal triangle is present, projecting back between the frontal carinae/antennal sockets (not well displayed in the present images displayed here, unfortunately).
- The antennal sockets are inclined such that the portion of the socket margin and torulus nearest the head’s dorsal midline are on a higher level (fig. 108).
- The frontal carinae are present as simple structures that only partially conceal the antennal sockets (fig. 104-105).
- The narrow neck that joins the condylar bulb of the antennal scape to the scape proper is straight.
- Eyes are present (figs. 100-103), and the antenna has 8-12 segments.
- A promesonotal suture is present (fig. 106).
- Metanotum present (fig. 107); note that the metanotum is present in the form of a metanotal groove separating the mesonotum and propodeum, the last vestige of the mesonotum on the dorsal alitrunk.
- Propodeal lobes are absent (fig. 106).
- Waist, or petiole, is of a single node (fig. 107).
- Helcium tergite dorsally with extensive U-shaped emargination of its leading edge, reaching back the major length of the sclerite (fig. 106).
- Abdominal segment 4 = gastral segment 2, without differentiated presclerites (not depicted).
- Pygidium, i.e., tergite of abdominal segment 7 = gastral segment 5, large and simple (not depicted).
- Hypopygidium, i.e., sternite of abdominal segment 7 = gastral segment 5, with a U-shaped to almost circular acidopore apically, which acidopore is equipped with a circlet of hairs (not depicted).
- Sting absent, replaced by acidopore (not depicted).
Sibling mating among the longhorn crazy ants is carried out in a way that prevents the genetic costs generally associated with inbreeding. Other organisms have also evolved adaptations that serve the same purpose, but the mode of reproduction observed with the longhorn crazy ant appears to be unusually novel. Here, the three castes of ants — workers, queens, and males — are all produced through different means (for a full explanation of these processes, see the article by Pearcy et al., linked to in the list of references below). Workers, for example, develop through normal sexual reproduction between queens and males, but queens are produced clonally, and are genetically identical to their mothers, while males — who, in a process similar to that of the females (who don’t inherit paternal alleles), never inherit maternal alleles — and thus are genetically identical to their fathers. This system, which ensures an absolute separation between queen and male genomes in the reproductive castes, prevents genetic inbreeding from taking place. This completely isolates the male and female gene pools, allowing queens to avoid the costs associated with inbreeding. That factor is thought to be a significant element in the ability of this species of ant to not only survive, but to thrive in dramatic fashion, wherever it is transplanted.
- Kingdom Animalia (ahn-uh-MAYHL-yuh) — first described in 1758 by the Swedish taxonomist Carolus Linnaeus (1707 – 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: see the detailed description of this subfamily below;
- 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 Formicinae (fohr-mih-SEE-nee) — first described in 1836 by the French entomologist Amédée Louis Michel le Peletier, comte de Saint-Fargeau (1770 – 1845), usually 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;
- Tribe Plagiolepidini (PLAH-gee-oh-lepp-uh-DEE-nee) — the identity of the taxonomist(s) who first described this tribe is obscure, but the term appears to be cobbled together from the Greek roots πλαγιος (PLAH-gee-ose) = “sideways” + λεπιδος (pron. LEPP-eh-dose) = “a scale” to refer to the character of the one-segmented scale of the petiole;
- Genus Paratrechina (pare-uh-TREK-en-uh) — first described in 1863 by the Russian entomologist Victor Motschulsky (1810-1871), using the Greek prefix παρα (PARE-uh) = at once + the Greek verb form τρεχω (TREK-oh) = to move quickly, run over + the Latin diminutive suffix -ina, in reference to ants that move quickly and erratically; the genus is recognized today as comprising over 150 species and subspecies; they are known generally to produce large colonies in open soil or under rocks and debris; many are distributed worldwide, and some are found on every continent of the world except Antarctica;
- Species longicornis (lawn-juh-KOHR-ness) — first described in 1802 by the French zoologist Pierre André Latrielle (1762 – 1833), using the Latin adjective longus = long + the Latin corneus = horn, in reference to an ant possessed with unusually long antennae;
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- 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.
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