Formosan Termites Swarm in Dripping Springs and Wimberley, Texas

This article by Jerry Cates, with thanks — for his contribution of specimens — to John Henry Bartose, was first published on 22 September 2012, and revised last on 18 November 2012. © Bugsinthenews Vol. 13:09(02).


Formosan termite (Coptotermes formosanus Shiraki); Dripping Springs, TX 13 Sept 2012; swarmers caught in spider web

001. Swarmers caught in spider web

Formosan termite (Coptotermes formosanus shiraki); Dripping Springs, TX 13 Sept 2012; swarmer caught in spider web

002. Swarmer in spider web


On 17 September 2012, upon arriving at a commercial building in downtown Dripping Springs, Texas [the nature of the commercial enterprise involved, and its exact location, are not divulged in this article in order to protect the privacy of the company’s staff and clientele] to conduct a scheduled periodic inspection and treatment program at that site, I was told that flying insects had lately been bothering the building’s employees while they were outside after sundown. The insects were present in large numbers, swarming around the outside lights and making pests of themselves. They didn’t bite or sting, but they were fairly large and quite annoying.

Let’s go take a look,” I said.

Sometimes, when quantities of insects show up at night, a few will die before daybreak, and their bodies will be left behind the next day. Outside, at one of the well-lit side entrances to the building, I found a few dead half-inch-long flying insects caught in spider webbing (fig. 001), their orange-brown wings spread as if in flight, exposing yellowish-orange bodies less than half the length of the wings (fig. 002). In answer to my question, the employee confirmed that these were, indeed, the insects that had been annoying everyone. And, no, they had never been seen here before, as far as the employee knew.

It happens that these are termites,” I said quietly, “but not ordinary termites… They look like Formosans. It isn’t surprising to see them anywhere in Central Texas these days, though I wasn’t aware that Formosan termites had made it to Dripping Springs already. Plus… they are swarming a bit late in the year, about two months late to be exact.

The employee stared at the ground, as if deep in thought, then straightened and said “Well, if these really are Formosan termites, then I have them at my house, too. The same night these showed up here — last Thursday, on 13 September — they also showed up at my home in Wimberley, about 9 miles due south.” That was interesting news. First, it suggested (and was later confirmed) that these termites only swarmed in massive numbers once, on 13 September, and only a few swarmers were found on subsequent nights, which is typical of termite swarms. Second, it told me the swarms in this general area took place on the same night, as much as nine miles apart. Though the termites came from separate colonies, they behaved in an identical fashion. Again, that was not surprising. In some years, I receive calls from all over Texas on the very same day, reporting swarms of our native subterranean termite species, almost always after a significant, sweeping, state-wide rainfall event has moistened most of Texas.

A few days later I paid a visit to the home in Wimberley and collected a number of Formosan termite specimens from a light fixture on the front porch. They looked just like the specimens obtained from the commercial building in Dripping Springs on September 17.

In both cases, heavy rains had occurred the day before, following a long, hot, dry spell that extended from early May through the first 11 days of September. Though Formosans usually swarm in May or June, they won’t swarm at all if conditions are not right, even if they want to. Hot, dry weather spells disaster for swarming termites, who mate and immediately search for a cool, moist place to start a new termite colony; if they fail to find a cool, moist place to bed down, they quickly die of exposure. Not surprisingly, if weather conditions are unsuitable during the normal swarming season for their species (the characteristic swarming season typically varies from one termite species to another), termites will often delay their swarming activities until favorable conditions occur. During the extraordinary drought of 2010 and 2011, such conditions were absent throughout the year in Texas and the surrounding states, so swarms of nearly all species of termites were sparse to nonexistent. That produced a latent swarm potential that, again in 2012, could not be activated during the normal swarming season but that, two months later, gave them an opportunity to swarm out of season. We’ve seen delayed swarms take place with other termite species under similar circumstances, so it’s not surprising to observe Formosan termites doing the same thing.


My experiences with Formosan termites…

Back in the 1990’s, while carrying out a series of experiments in New Orleans and Metarie (a New Orleans suburb), Louisiana, I’d become intimately familiar with the Formosan termite and its habits. Those experiments were specifically conducted to test a number of termite control devices I had designed against the most feared subterranean termite known to man. Because those termites — known as Formosans — were literally as thick as flies in the New Orleans area during their swarming season (normally May and June of each year), that was the premier place to go to test new, innovative termite control solutions. If a detection and control device worked against Formosan termites, it could also be counted on to work against practically all the other subterranean termite species found in North America.

My experiments with Formosan termites were conducted in conjunction with a much larger set of experiments and studies, begun in 1987, with native subterranean termites at sites scattered throughout Texas. Besides providing me an excellent education in termite biology, that work culminated in a number of patented termite detection, concentration, and control devices (e.g., U.S. Patent 6178834), but at an extremely high cost. Like many inventors, I learned that designing and patenting novel devices is the easy part; marketing it to a competitive world in a timely fashion is more difficult, eminently more costly, and potentially all-consuming. When the market for termite control devices tumbled in the early years of the new millennium, I reluctantly allowed all my patents to expire, resumed more productive pursuits, and moved on. I’ve continued, however, to make proprietary improvements to the devices themselves, added more devices to the mix, and developed a line of non-toxic habitat modifiers. Today those devices and habitat modifiers play important rôles in all the pest management work I perform throughout the state of Texas.


Formosan Termites in Texas…

Formosan termites are easily transported, unwittingly by man, from one place to another. Since they thrive below the 35th parallel, they will likely expand all the way to the Red River and — in the panhandle — to within spitting distance of Amarillo. As long as average temperatures and moisture conditions on the peripheries of their present infestations are suitable, they will expand their territories every year.

The first Formosans to arrive in the U.S. apparently entered through the ports of Houston, New Orleans, and South Carolina in the 1960’s, in cargo shipped from Asian ports. As those imported termites became established in their new locales, they slowly moved outward to new locations nearby. Often their expansion was gratuitously aided by man, chiefly through the movement of infested timbers and other cellulose-containing materials. We knew it was inevitable that they would one day be found throughout much of South, Central and East Texas. When, in the early years of the new millennium, swarms of Formosan termites were observed in the inland Texas cities of Austin, Dallas, Fort Worth, and San Antonio, investigations were conducted to determine the most likely means by which they got there. Though it was impossible to account for every situation, the primary route appeared, at that time, to have been through the movement of used railroad ties. The ties, collected from locales along the Gulf Coast, were transported to inland cities where they were sold for use as inexpensive landscaping timbers.

Though railroad ties are pressure treated with creosote and other preservatives that are lethal to wood-destroying insects and fungi, the preservatives leach out of the wood over time, eventually to the point that the wood becomes vulnerable to termites and fungi. The wood at the center of the tie, which contains the lowest concentration of preservatives, is attacked first, as aging ties develop deep cracks that provide easy access by wood destroying agents to their interiors. Hidden from view, the termites deep inside infested railroad ties do little to make their presence known, and those who trade in used railroad ties easily become their unknowing distributors. At each new location, the infested ties are incorporated into landscaping projects throughout the area, potentially leading to infestations of entire cities within the span of a few short years.


Should The Sites Mentioned in this article Be Treated for Termites?

In general, unless and until actual termite infestations are observed inside a structure itself, the need to treat a structure for termites simply because termite swarms have been observed in the vicinity is open to serious question. In fact, prior to the 1990’s, and especially before the chlorinated hydrocarbon termiticides were banned in 1987, an exterminator who recommended a preventive termite treatment, based solely on the observation of a nearby termite swarm, risked being accused of unlawful coercion. After 1987, however, as the limitations of the termiticides initially brought on the market to replace chlordane and heptachlor became known, the logic and legality of preventive termite treatments gained traction. That traction continues to grow despite improvements in the efficacy of modern termite control products, particularly in the face of the looming threat of several recently introduced and unusually destructive termite species, specifically the Formosan (Coptotermes formosanus) and Asian (C. gestroi) termites.

Whether or not preventive termite treatments should be carried out at a given site is now more a factor of the quality and quantity of the information at the disposal of those responsible for the structures at the site. The pest manager’s job, initially, is to collect, analyze, and present all the relevant facts. If, in the pest manager’s opinion, the facts warrant consideration of preventive, proactive, or remedial treatment regimens, the alternatives available and the costs associated with them should be described in full detail, in accordance with applicable laws, and presented in accord with the documentation standards mandated by governmental regulatory agencies (in Texas, the Texas Department of Agriculture, Structural Pest Control Service). It is then up to the responsible parties to decide how to proceed from there.

For example, had the termites that swarmed here been nothing more than the usual native subterranean termites found throughout Central Texas, I would most likely not recommend aggressive preventive treatments at the structures involved. I would, however, counsel strongly in favor of thoroughly inspecting for conditions conducive to termite infestations, followed by a plan of correction to resolve all of the conducive conditions that such inspections revealed. Further, I’d urge those responsible to consider, at minimum, preventive treatments of all plumbing penetrations within the structures.

But, as already noted, these swarms were not of ordinary, native subterranean termites. Swarms of Formosan termite reproductives (which are notoriously poor fliers) originate from active infestations that are usually no more than 150 feet away. The commercial site in Dripping Springs is more than twice that distance from any off-site man-made structures, so the likelihood of an existing but undetected infestation of part of the on-site commercial structure itself is not insignificant, and at least one major conducive condition was found on-site that may well be the locus of at least one, and possibly several, such infestations. Even if that is not the case, however, these swarms signify the definite fact that Formosan termite reproductives have mated here, shed their wings, and entered the nearby soil to lay eggs in an effort to produce new soil-based Formosan termite colonies. Worse, the soil here provides a perfect medium for termite colony development, as evidenced by the discovery of numerous mature colonies of another, non-destructive termite species in the Termitidae family, that is inhabiting the soil of the grounds at this site (which will be the subject of another article, now in process).

The likelihood that some of the nascent Formosan termite colonies at this site will proceed to full-blown, well-established colonies is relatively high. Once established, Formosan termite colonies are capable of causing devastating damage to structures soon after their infestations commence, i.e., often within one to three years. Because of this fact, homeowners and business owners must give careful consideration to the practicality of having their sites treated proactively to stop or blunt the threat of Formosan termite infestations before they get started. An important part of the proactive programs that must be put in place at any site threatened with termite infestations is the process of habitat modification, or the elimination of all known conditions that attract or nurture termites at the site. But habitat modification is, as I mentioned, a process, rather than an event. The sooner that process is begun the better.


Treating Formosan Termites in Central Texas

Treatment procedures for Formosan termites are essentially the same as those for our native subterranean termite species. Those procedures involve three distinct steps, in a process that continues into the future in accordance with the regular schedule defined in step III:

Step I: The ordinary processes of (1) placing baits strategically around the perimeter of the structure, (2) treating the soil in places where soil toxicants are appropriate*, and (3) treating the at-risk portions of the structures involved (3a) proactively and — if termite infestations are found inside the structure — (3b) remedially.

* Note: Many professional pest managers, myself included, feel that the use of soil toxicants is inappropriate in light of the risks involved and the availability of effective termite baits that make the use of soil toxicants unnecessary. Thus, although a variety of soil toxicant products are presently approved and marketed for termite control, I avoid their use entirely.

Step II: Habitat modifications, inside the structure, around its perimeter, and within the entire treatment site, to reduce and even eliminate the risks of termite attraction and nurturance. Because every site and its associated structures differ in so many ways, it is difficult to lay out a complete set of specifics that applies to every case. The specific habitat modifications appropriate to a given site, however, are easily discoverable by those experienced in termite control, and are also easy to describe. Those that apply to the two sites discussed in this article — one in Dripping Springs and the other in a residential subdivision in suburban Wimberley — will be discussed in detail as this article progresses and as the work is performed.

Step III: Follow-up inspections and treatments, as part of a regularly-scheduled program, to ensure that all treatment programs remain viable and in-force, that all habitat modifications performed in the past continue to serve the need to obviate all risks of termite attraction and nurturance, and that nothing at the site is allowed to introduce new, unmitigated risks of that nature.


Note that the photographs below, taken of specimens collected at the sites described in this article, may be enlarged for more detailed viewing by placing your cursor over them and clicking:

Formosan termite (Coptotermes formosanus shiraki); Dripping Springs, TX 13 Sept 2012; swarmer

100. Formosan swarmer

Formosan termite (Coptotermes formosanus Shiraki); Dripping Springs, TX 13 Sept 2012; swarmer body ventrum

101. Swarmer body ventrum

Formosan termite (Coptotermes formosanus Shiraki); Dripping Springs, TX 13 Sept 2012; swarmer head capsule

102. Head capsule

Formosan termite (Coptotermes formosanus Shiraki); Dripping Springs, TX 13 Sept 2012; right forewing venation

103. Right forewing venation

Formosan termite (Coptotermes formosanus Shiraki); Dripping Springs, TX 13 Sept 2012; right forewing hairs

104. Wing pubescence


Anatomy: Formosan termites exhibit a distinctive set of anatomical characters. Typically we’d describe all castes but, because — in the case before us — only winged alates are presently available from the two sites under discussion, this discussion will be limited to the winged reproductive caste. As shown in fig. 100, the winged alates observed here were about 17 mm in length, from head to wingtip. This is somewhat longer than the typical Formosan alate, which is generally 14-15 mm in length (Sheffrahn 2011). I of course attribute the difference to the fact that these are Texas Formosans. Note that the body (fig. 101) is about 7.5 mm in length. The width of the head capsule (fig. 102) spans almost exactly nine graduations on the scale above the head; that scale, taken from an ink-jet printer (where, prior to being enlisted as an aid to microscopic measurement, it had metered the movement of a stepping motor) measures 0.1667 mm per graduation; thus the head capsule is almost exactly 1.5 mm wide, as would be expected (Sheffrahn 2011) for a Formosan alate; thus, though a Texan, it (as is the case with all good Texans) has not allowed that fact to go to its head. The right forewing shows two pigmented veins in the costal region — a marginal costal vein, in parallel with a radial sector vein, connected by transverse veins distally — as described for Coptotermes formosanus by Sheffrahn et al., 1994, p. 472.



  • 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;
  • Subclass Pterygota (Lang, 1888) — ;
  • Infraclass Neoptera (Wulp 1890) — first described in 1890 by the Dutch zoologist F. M. Van der Wulp, using the Greek words νεος (NEE-ose) = “young, youthful, new, fresh” + πτερον (TARE-on) = “a feather, wing, fin” to distinguish the winged insects in this infraclass — whose wing morphology is more recently evolved and enables them to be folded over the abdomen in such a way that, when at rest, the wings are generally inconspicuous — from the more primitive winged insects in the Paleoptera (an infraclass that appears to be paraphyletic and is now undergoing significant taxonomical scrutiny and revision, not without some attendant controversy) whose wings cannot be so folded and thus remain conspicuous and somewhat encumbering of the resting insect; this infraclass includes most of the winged insects of today, excluding the mayflies, dragonflies, and damselflies;
  • Superorder Dictyoptera — from the Greek words δικτυον (DICK-ty-ohn) = “a net” + πτερον (TARE-on) = “a feather, wing, fin” to refer to insects with membranous, net-like wings; includes three groups of polyneopterous insects, namely the termites, the cockroaches, and the mantids;
  • Order Blattodea — from the Latin term, blatta = “cockroach”; the order, today, includes all cockroaches and all termites, the latter having been transferred from the order Isoptera (of Greek origin, meaning “equal wings”) when modern molecular genetics confirmed the long-held suspicion that termites and cockroaches were intimately related in taxonomical terms;
  • Superfamily Blattoidea [syn. Termitoidea (Latreille, 1802)];
  • Epifamily Termitoidae — from the Latin word, termes = “wood-worm”;
    • Family Mastotermitidae (Froggatt 1897) — the most primitive of all extant termites, comprised of a single genus and species, Mastotermes darwiniensis (Froggatt 1897), and found only in Northern Australia;
    • Family Kalotermitidae (Banks 1919) — drywood termites, consisting of 22 genera and 419 species of termites that infest dry timbers and that do not require a connection to the soil to survive (Mallis 2011);
    • Family Termopsidae (Grassè 1949) — dampwood termites, consisting of 5 genera and 22 extant species of termites that infest moist wood, usually in forest regions where they perform beneficial processes that reduce fallen timbers to soil, but that sometimes infest structures due to excessive moisture and wood-to-ground contact (Mallis 2011);
    • Family Hodotermitidae — rottenwood termites, comprised of 3 genera and 19 species that, like the Termopsidae, infest damp, rotten wood;
    • Family Rhinotermitidae (Froggatt 1897) — subterranean termites, comprised of 345 species that generally require a connection to soil to thrive, but including several genera, e.g., Coptotermes, that do not absolutely require a soil connection if moisture conditions in the cellulose they are feeding upon are sufficient;
    • Family Serritermitidae (Hagen and Bates) — a primitive, monotypic termite family that includes a single, small, rare, bizarre species, Serritermes serrifer (Hagen and Bates), known only from three localities in Brazil.
    • Family Termitidae (Latrielle 1802) — higher (more recently evolved) termites, comprised of seven subfamilies;
  • Family Rhinotermitidae (Froggatt, 1897) — first described by the Australian economic entomologist Walter Wilson Froggatt (13 June 1858 – 18 March 1937), who combined the Greek word ρινος “RYE-nos” = skin or hide + the Latin word termes = a wood-worm, to refer to a wood-destructive organism whose colonies reside within a tough outer skin-like structure of their own making; the family includes 16 distinct genera, and approximately 345 known species;
  • Genus Coptotermesfrom the Greek word κοπτω (KOPP-toh) = “to strike, smite, cut off” + the Latin word termes = “wood-worm”, a possible reference to the ability of massive numbers of the termites in this genus to cause devastating damage to sound wood by breaking off small pieces of the wood with their mandibles;
  • Species Coptotermes formosanus (Shiraki, 1909) — first described in 1909 by the Japanese entomologist Tokuichi Shiraki, who happened upon the species in the Formosan city of Taipei; the species is native to southern mainland China, and had been introduced to Formosa centuries earlier, possibly by hitching a ride with traders;




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