Colobopsis papago

This species nests in dead limbs of oaks (Quercus emoryi, Q. oblongifolia), or mesquites, and are difficult to find. They are most common in the stubs of broken branches, with a diameter of 4 cms or more, and point vertically (apparently catch more rainwater). The nest has several entrances, which are blocked by the large, round, truncated portion of the heads of majors (see figure in Creighton, 1967). They move to allow the minors to exit and enter the nest. Creighton (1967) wrote one of the most interesting articles ever written on ants for a general audience, and is well worth reading. When the majors are disturbed, they exude a sticky, gray fluid from the region of the mouth (probably mandibular glands?), which spreads over the truncated portion of the head. It dries to a crust, which is difficult to remove. Mating flights occur throughout July, during the first half of the rainy season. Workers apparently forage at night, as they are not found on during the day on trees which contain nests. (Mackay and Mackay 2002)

Identification
Recognizable by the truncate anterior part of the head of the major, which is nearly perpendicular to the long axis of the head as seen from the side. C. papago nests in dead branches. The minors can be difficult to separate from similar species (Camponotus ulcerosus). The metanotal suture is depressed in C. papago but is not in C. ulcerosus. (Mackay and Mackay 2002)

Distribution
United States, southern and southeastern AZ. Mexico, Sonora.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Habitat
Oak and mesquite forests.

Biology
Creighton (1953) - Before concluding this paper I wish to present an account of the habits of C. papago. The ten colonies taken to date have all come from evergreen oaks or mesquite trees. The two oaks involved are Quercus emoryi and Q. oblongifolia. Most nests are constructed in the stubs of broken-off branches which have a diameter of an inch and a half or more. The thickness of the stub seems to be more important than its length. I have taken colonies from stubs less than six inches long but I have yet to see one in a branch that was small enough to be considered a twig. Inside the stub are numerous, narrow passages which roughly parallel the grain of the wood. Several openings lead from these to the outside. It is evident that in a fully developed nest of papago there must be several "janitors" on duty at the same time. As mentioned above, this ant does not ordinarily nest in twigs. At first I supposed that this reaction might be due to a scarcity of trees which have twigs with a suitable central pith cavity and this may be a part of the explanation. But it now seems certain that moisture plays a large part in the choice of nest site. I had realized that papago usually nests in limb stubs which point upward long before I saw any significance in this response. But on one occasion I was examining limb stubs immediately after a heavy and prolonged rain storm. I found that the stubs which pointed upward caught and held the rain water much as a cistern would. Rain soaked into the fractured upper end of the stub and accumulated at its lower end. The lower end was often so wet that water would drip out of it after the stub was knocked loose from the tree. In contrast, the horizontal stubs and those which pointed downward caught far less rain. The latter were often quite dry inside, despite the fact that they had been drenched with rain for several hours previously. It thus appears that the female of papago, in choosing a nest site in limb stubs which point upward, takes advantage of a natural system of water conservation. This could certainly be one reason why the nesting habits of papago differ from those of the eastern twig-dwelling species. It may be added that the preference of this ant for nesting in the stubs of broken-off limbs seems to be one factor which has kept it out of the hands of collectors. It was some time before I realized that the most important piece of equipment needed to collect C. papago is a heavy axe. The nests are almost always built in sound, hard wood and it is not easy to get the insects out, even after the stub has been knocked loose. The ants which are in the lower passages can often be jarred out by whacking the stub with the back of the axe. But to get all of them the stub must be split into pencil-sized pieces. Anyone who makes a practice of collecting papago will never lack for exercise.

In addition four more colonies were secured near Perkins Ranch in Brown Canyon on the eastern slope of the Balboquivari Mountains. These last colonies were situated at elevations between 4100 and 4600 feet. Mention has already been made of the single colony taken in Garden Canyon in the Huachuca Mountains. The elevation of the station from which this colony came was 5800 feet. Since the above was written nests of C. papago have been taken by the writer in Cottonwood Canyon, Peloncillo Mts. (4800'), Arizona and fourteen miles north of Imuris, Sonora (3200'), Mexico. In both cases the ants were nesting in Q. emoryi.

The majors of C. papago, when disturbed, have a curious habit of exuding from the mouth a sticky, greyish fluid. This often spreads backward over the truncated portion of the head. If it is allowed to dry there it forms a crust that is almost impossible to remove. As to what the use of this fluid may be is hard to say. It may have repellant characteristics for other ants and thus serve as a defensive mechanism which the major employs when acting as a janitor at the nest entrance.

It is safe to infer that C. papago forages at night. Although I have examined hundreds of oak and mesquite limbs, some of which later proved to contain flourishing colonies of papago, I have never seen a worker outside the nest. This foraging must be a slow business, for papago is a rather sluggish ant. The minor workers can move with fair speed but the majors are so slow that it is easy to pick them up. Finally, the marriage flight of papago occurs throughout the month of July. In an ordinary year it would thus take place during the first half of the summer rainy season.

Nomenclature

 *  papago. Camponotus (Colobopsis) papago Creighton, 1953c: 153, figs. 1, 2; pl. 13, figs. 1-3 (s.w.q.m.) U.S.A. Combination in Colobopsis: Ward, et al., 2016: 350.

Worker
Major Head 1.06 mm., thorax and petiole 1.5 mm., overall length 4.5 mm.

Truncated portion of the head distinctly concave, with a low, serrate flange bordering either cheek but not continued across the top of the clypeus. The entire clypeus raised slightly above the level of the adjacent portions of the cheeks, which slope downward to the clypeus from the bordering flange. Sculpture of the truncated portion of the head consisting of coarse, irregular ridges which form reticulations. These reticulations and the areas which they surround, are covered with numerous, very fine, crater-like punctures. These punctures do not dull the shining surface. Sculpture on the mandibles rough but not distinctly reticulate. Seen from above the frontal lobes are covered with even reticulations which surround circular or nearly circular depressions. This reticulate sculpture extends almost to the level of the single median ocellus, with the depressions becoming shallower and more widely spaced towards the rear. The rear third of the head is finely shagreened and notably more shining, particularly at the occipital corners, than is the heavily sculptured front of the head. The reticulation on that part of the clypeus which lies behind the truncation is much less even than that on the frontal lobes. Reticulation on the cheeks less even and somewhat coarser than that on the frontal lobes. The entire anterior half of the head with the same fine, crater-like punctures which occur on the truncated portion. A very feeble frontal furrow is visible in certain lights. Antennal scapes rather strongly shining with small, white, appressed hairs. Hairs on the truncated portion of the clypeus and on the front face of the mandibles very strongly clubbed and shaped like tear drops. Hairs along the outer border of the mandibles, on the frontal lobes and on the sides of the head behind the truncation long, curved, blunt and often clavate but rarely as strongly clubbed as those of the clypeus.

Thorax, petiole and gaster more finely shagreened than the head with the surface strongly shining. In addition to the shagreening there are very small scattered punctures present, from which arise short, delicate, fully appressed hairs. No erect hairs present on the thorax, those on the crest of the petiole very short and fine. Erect hairs rather sparse on the gaster, mainly confined to the row at the posterior edge of each segment. Legs finely shagreened and strongly shining with delicate, appressed hairs like those of the thorax. Fore femora expanded dorso-ventrally and strongly compressed laterally. The tarsal joints and the funiculi covered with abundant, short, yellowish, semierect hairs. Color deep blackish brown, the anterior third of the head clear yellowish brown. Tarsi, funiculi, base of the petiole and the slltures of the thorax light brown.

Minor Head 0.9 mm., thorax and petiole 1.25 mm., overall length 3.25 mm.

Head, seen from the front, with the eyes notably more convex than those of the major, the sides in front of the eyes narrowing to the insertion of the mandibles. Mandibles with four well-developed teeth. Clypeus moderately convex from side to side, somewhat more strongly convex from front to rear, ecarinate or with a very blunt and indistinct carina. Frontal lobes together forming a trapezoidal area which is a little wider behind than in front. Frontal groove absent. Occiput evenly convex, the lateral portions meeting the posterior border of the eyes without any distinct posterior angles. The antennal scape, when extended straight to the rear, surpasses the occipital border by an amount slightly less than its greatest thickness. Head, thorax and abdomen moderately shining with a rather strong, reticulate shagreening. Appressed hairs as in the major and female. Erect hairs long, tapered and with sharp tips. They are rather numerous on the mandibles and clypeus, sparser on the front and represented on the occiput by a single pair. Thorax without erect hairs. Crest of the petiole with several very short, delicate erect hairs. Erect hairs on the gaster widely and rather evenly spaced over the dorsum except at the base of the first segment, which is hairless. Fore femora laterally compressed as in the major. Color: blackish brown, the mandibles and tarsal joints light brown.

Queen
Head 1.25 mm., thorax and petiole 2.3 mm., overall length 6.0 mm.

Head similar to that of the major but with all three ocelli large and prominent. Sculpture on the truncated portion of the head identical with that of the major. Reticulate sculpture on the frontal lobes smaller and shallower than that of the major and not extending as far back on the head. Eyes distinctly larger and more convex than those of the major. Hairs on the mandibles and the truncated portion of the clypeus longer and less clubbed than those of the major.

Thorax feebly shagreened and rather strongly shining, with small, scattered, appressed hairs as in the major. Erect hairs absent on the thorax except for a pair of long, yellowish hairs which arise from the scutellum. Gaster more feebly shagreened and more strongly shining than the thorax but with similar appressed hairs. Erect hairs on the gaster only moderately abundant, mostly confined to a row at the rear of each segment. Erect hairs on the terminal gastric segment distinctly longer than those elsewhere. Fore femora laterally compressed as in the major. Color blackish brown, the anterior quarter of the head, much of the scutum and the middle and hind tarsi yellowish borwn. Wings hyaline, iridescent and with pale yellowish veins.

Male
Head 0.7 mm., thorax 1.5 mm., overall length 3.5 mm.

The sides of the head in front of the eyes taper slightly from the anterior edge of the eye to the insertion of the mandible. Behind the eyes the sides of the head are evenly convex from the rear edge of the eye to the lateral ocellus. The occipital border is slightly concave between the lateral ocelli. Anterior border of the clypeus feebly sinuate. Mandibles small, somewhat spatulate and with the teeth represented only by a v-shaped notch on the masticatory margin. Antennal scapes long, surpassing the occipital margin by a little more than one-third their length.

The greatest width of the thorax, when seen from above is approximately equal to that of the head. In profile the neck of the pronotum is short, the anterior face of the scutum is evenly rounded and its dorsal face is flat and on the same level as the anterior edge of the scutellum. The latter is convex in profile and descends sharply in the rear. In profile the epinotum is depressed well below the level of the scutellum, rounded and without a good separation between the basal and declivious faces. Petiole with a short but distinct anterior peduncle, the node low in profile, tapering slightly from base to crest with the latter evenly rounded. Seen from above the node of the petiole is transversely oval, with the width about twice the thickness from front to back. Gaster approximately as long as the thorax. Genitalia small and obscure.

The surface is moderately to strongly shining. Front and genae strongly shining with scattered punctures. Occiput and scutum less shining with a delicate reticulate sculpture. Scutellum very shining with scarcely any sculpture. The remainder of the thorax and the node of the petiole with a reticulate sculpture which is less pronounced than that of the scutum. Gastric sculpture very feeble, shagreened but scarcely reticulate, the surface more shining than that of most of the thorax. Sparse erect hairs are present on the head, the coxae and the gaster. Thorax without erect hairs. Antennal scapes, the femora and the tibiae with very delicate, short, sparse hairs which are fully appressed. Pubescence on the antennal funiculi and the tarsal joints suberect and not parfticularly prominent. Thorax and gaster dirty, yeHolwish brown, the head distinctly darker. Wings hyaline and iridescent with the veins very pale.

Type Material
Types of female, male, major and minor worker deposited in the Museum of Comparative Zoology, Cambridge, Mass. The type locality is Forestry Cabin (Balboquivari Canyon), Baboquivari Mts. (3500'), Arizona. The type nest was taken on July 24, 1951 in Quercus emoryi. Four other colonies were taken in this same station.

Etymology
Named for the Papago people. Creighton found these ants while working on what was then the Papago Indian Reservation at Sells, Arizona. The Papago are today known as the Tohono O'odham, and the reservation is the Tohono O'odham Nation.

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Johnson R. Personnal Database. Accessed on February 5th 2014 at http://www.asu.edu/clas/sirgtools/resources.htm