Blepharidatta conops

A cerrado and caatinga vegetation inhabitant that can be quite abundant in some areas of its range. Ergatoid queens of B. conops have head disks that can be used for phragmosis, the first known case of this defensive behavior to be employed by a non-worker caste.

Identification
Brandão et al. (2015) - Comparatively large (total length 45–47 mm). Body chestnut to blackish, with always lighter, sometimes reddish, gaster. Body mostly shiny, feebly areolate and irregularly rugulose. Eye evidently protruding and conical. Propodeal spine shorter than petiole in lateral view. Petiolar node weakly elevated, long and cylindrical.

Kempf (1967) - Following are the characters that distinguish conops  from Blepharidatta brasiliensis: larger size; darker color; pilosity more abundant with hairs present also on ventral surface of petiole and postpetiole; clypeus with a pair of prominent tubercle; vertex with a broad sagittal furrow flanked by a pair of low and diverging ridges; occiput separated from vertex by a carina; dorsum of head lacking longitudinal rugae; occipital corners broadly and obliquely truncate and bidentate; eyes strikingly conical; antero-inferior corner of pronotum bidentate; epinotal spines relatively shorter, less approximated at base and less diverging at apex; infraspinal lamella with an upper spine and a median lobe; petiole rather cylindrical than clavate without a differentiated node; gaster entirely covered with microsculpture, never partly smooth and shining. According to Wheeler (1915: 485) brasiliensis has only 4 teeth on chewing border of mandibles. But according to my observation, both brasiliensis and conops have 5 mandibular teeth.

Distribution
Blepharidatta conops has been recorded in different central Brazilian states, mostly those covered by cerrado or caatinga vegetation: western Bahia, southwestern Ceará, Goiás, Maranhão, Minas Gerais, Mato Grosso, Mato Grosso do Sul, Piauí and Tocantins. (Brandão et al. 2015)

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
Brandão et al. (2015):

This is the most well studied  Blepharidatta  species, having been the subject of several published studies by the Museu de Zoologia da USP team. In a series of papers, Brandão, 2000, Brandão et al. 1998, 1999, 2000, 2001, 2008; Diniz et al., 1998; Silva, 2003, Silva & Brandão, 2001, and Silva et al., 2001, 2002, published detailed biological observations on B. conops, briefly summarized below.

Jorge L. M. Diniz studied 71 nests of B. conops at Chapada dos Guimarães, Mato Grosso, Três Lagoas and Selvíria in Mato Grosso do Sul (Diniz et al., 1998). Pereira et al. (2014) studied a population of B. conops with 29 nests in Crateús, Ceará state. All but one of these nests were excavated in the soil; one odd nest also occupied part of a hollow dry branch fallen on the soil. Nest populations varied from a few individuals to a maximum of 248 workers in the savannas and 437 in Ceará, and only one nest contained two ergatoid gynes; all other are monogynous, although in some nests no gynes were recorded, possibly missed during excavation. Blepharidatta conops nests are easily spotted by the carcass ring the workers carefully arrange around the nest opening. Once one gets used to this search image, it becomes extremely easy to spot the nests. The carcasses around the nest opening are similar in nature to those found in the bottom chamber of the nest; field and laboratory observations suggest the workers collect live arthropods or carcasses, bring them inside the nest for larval feeding, and then put them in the carcass ring around the single nest opening. Populations are rather dense, although separated sometimes by several kilometers, reflecting the low dispersal ability of ergatoid gynes.

Pereira et al. (2014) argue that B. conops populations from Ceará could represent a distinct although closely related species, mostly because of the almost flat anterior cephalic disks of Ceará ergatoids and because this population was collected in a locality within the semi-arid Caatinga, while other B. conops populations come from central Brazil savannas. Brandão et al. (2001) already noticed the extreme variation in the sculpture of the ergatoid gynes frontal disc, but were not able to find a single case in which two forms occur sympatrically. They related this variation to the ergatogyny of the gynes that enhances the genetic viscosity of populations, resulting in local variants. In the case of the Ceará population, the ergatoids show the same sculpturing pattern as in other localities, composed by polygonal units separating punctuated areas, although the sculpture units are not so densely packed in some regions of the disc as in other places, rendering the head and pronotal front more regular (see discussion and figures in Brandão et al. 2001). Moreover, we studied worker larvae of cerrado and caatinga populations, confirming the morphological identity of the immatures. Pereira et al. (2014) also described the striking similarities among B. conops populations and that of Crateús, Ceará, in nest architecture, in prey diversity found inside nests and the carcass rings, preferred daily time for foraging activities (with two peaks of activity), and other traits. Additionally, the measurements of the Ceará workers and gynes fall well within the range of other B. conops population measurements. We see no evidence of the existence of a different Blepharidatta species in Ceará.

Brandão et al. (2001):

Diniz et al. (1998) observed Blepharidatta conops populations in Selvíria, MS, Brazil, and found only one wingless queen per colony. We consider these to be ergatoids because their wing buds never develop. B. conops workers forage outside the nest during daylight hours, avoiding the warmest period, although a few workers stay out of the nest all day long. Some 30–35% of the workers in each colony are foragers, searching for live arthropod prey and carcasses (mostly ants) in a circular area with an average radius of 1.5 m around the nest opening. B. conops nests are aggregated in dense populations with more than 30 nests recorded in an area of 144 m2. Mature nests take the form of an almost vertical 20 cm deep channel, not much narrower than the 2 cm diameter opening, and ending blindly in a cone-shaped widening at the bottom. In mature nests, a subsidiary horizontal chamber opens at the midlength of this main channel, where the ergatoid queen and the brood remain most of the time (Figs. 1a and b).

The 2001 study included observations of more than 100 nests in the field, from four Brazilian states, with a majority of these then brought into and housed in artificial laboratory nests for observation. Their findings include:

B. conops nests contain on average 200 workers, immatures, and a single queen. The nest structure is quite simple, consisting mainly of a blind-ended cylindrical vertical tunnel up to 20 cm deep, excavated directly in the ground, although some nests occupy spaces under the bark of fallen tree trunks. Inside the main tunnel and, especially, in the bottom enlargement, we have found grass fragments or whole blades, seeds, spider and insects corpses.

We have never found carcasses or even fragments inside the subsidiary chamber, except during the short time when the carcasses are offered to the larvae; as soon as the larvae stop feeding, the carcasses are removed (Diniz et al., 1998). Sixteen out of 26 nests excavated in Selvíria housed myrmecophile visitors either in the bottom enlargement or along the nest walls, belonging to Isopoda (6 nests), Diplopoda (6 nests), pseudoscorpion (1 nest), Lepismatidae (2 nests), Japygidae (1 nest), and Diptera larva (1 nest), either alone or in combination. Five out of the fourteen nests dissected in Serranópolis housed myrmecophile visitors, also either in the bottom enlargement or along the nest walls.

Diniz et al. (1998) described the nest development of B. conops in uniform soils. Mature nests (Fig. 1a) differ from incipient nests in that the entrances of older nests are completely surrounded by a “carcasses ring”. Our recent observations in different localities have shown that nests that are constructed in non-uniform or rocky soils (Fig. 1b) differ from nests excavated in uniform soils in being more irregular in shape. Nests excavated in all kinds of soil are composed of a single cylindrical structure, the sum of all sections attaining also some 20 cm in depth, and, most importantly, all B. conops nests exhibit the same kind of architecture, containing a single subsidiary chamber linked to the main nest by a tunnel.

A comparative study of the composition of the carcass rings in different localities confirms that they are composed of the same material found inside the bottom enlargement of the nests, that is, mostly large pieces of arthropod corpses, as can be seen in Fig. 1 of Diniz et al. (1998). These authors have also described the frequent emigration of colonies to new nests; on average each colony moves to a new nest every 4 months. Before moving, workers excavate several provisional new nests in the vicinity of the older nest; ultimately one of these is chosen, and the workers transport immatures and the queen to the new location.

As the nests mature, workers prepare or select fine-grained debris, mainly very small fragments of the arthropod carcasses (coxae, antennae, etc.), and construct from this a wall at the beginning of the tunnel (wider at its superior margin than at the bottom; see Fig. 1d). At the bottom of this wall they leave a circular opening, small enough to accommodate exactly the queen’s frontal disk (Fig. 1c). The structure and composition of the carcass wall is unrelated to soil type; the wall is always made from relatively small pieces of carcasses, much finer than the pieces composing the entrance ring or those found at the nest bottom enlargement. The position of this wall within the nests does not facilitate direct observation of ergatoid behaviour, but our indirect evidence suggests the ergatoid queen blocks the entrance to the chamber with her very much-modified frontal disk.

After construction of the carcass walls in both laboratory nests, the queens were never seen outside the subsidiary chambers, while in nests where the walls were not constructed or were incomplete, ergatoid queens frequently visited the main tunnel. The queens in wall bearing nests were observed beneath the carcass walls for long periods, that is, they could not be seen at the subsidiary chamber; as said before, the artificial nest structure prevented direct observation in these instances. The shape and diameter of the wall passage matches the shape and diameter of the queen’s frontal disk, as will be explained below. In Figs.1c and d we present our interpretation of the “carcass wall” structure and how the queens block the entrance of the chamber.

Figure 3a presents an scanning electron micrograph of the frontal disk of a queen collected in Campinaçu in frontal view. Note that the anterior slope of the pronotum and head disk share the same sculpturing pattern. In Fig. 3b, we present a scanning electron micrograph of the anterior end of a queen collected in Selvíria, in side view, showing the compound eyes (not visible in the frontal view), the extreme enlargement of the frontal carinae over the antennal scrobe, and the shape of ther head and pronotal margins (respectively anterior and posterior) that enables the head to lock against the pronotal anteroventral face. The similarly sized, regularly spaced, stiff hairs protruding laterally from the perimeter of the head and pronotum anterior slope may help the queens to keep the anterior end in position while blocking the entrance of the tunnel.

Queens from different localities differ not only in size, but also in the sculpture of the frontal disk, although in a given population the ergatoids are very similar to one another. Workers and males from the different localities do not differ so dramatically.

Nests release males from August to February (Diniz, unpub. field observations), although in laboratory colonies males are produced year round. On one occasion we found a dealate male inside the main tunnel of a field nest – a syndrome often associated with nomadic ant species (Hölldobler and Wilson, 1990). In the laboratory, males actively search for nests, and, when close enough, are brought inside by groups of workers. We have never observed more than one male in a nest at a time. Inside the nest the male is groomed by workers and meets the virgin queen near the nest entrance, where copulation takes place.

Nests often house one or more myrmecophiles. In five out of 26 nests excavated in Selvíria we found larvae and adult Histeridae beetles either in the bottom enlargement or along the nest walls; in addition to histerids, two of the nests also contained pseudoscorpions and diplopods (Diniz, 1994). B. conops larvae are held in the mandibles of the workers positioned along the nest wall or laid on the floor of the subsidiary chamber, but are never found in the widened bottom chamber. B. conops workers feed their larvae by trophallaxis, after chewing the corpses or fragments of the arthropod prey and some vegetal material. Diniz (1994) observed histerid beetles taking full grown larvae from workers’ mandibles. The recovery of larvae by the workers is made impossible by the beetles’ behaviour; after “stealing” a larva, a beetle “crouches” over it, bending its legs under the carapace, and thus assuming the format of an almost perfect half sphere. The beetles’ smooth integument prevents their removal from the nest by the ants.

Queens actively walk throughout the nests. However, in nests where we found myrmecophiles such as histerid beetles, the majority of the ants immatures were located in the subsidiary chamber. In the presence of predators, the queen uses her extremely modified anterior end to block the entrance of the tunnel wall that leads to the subsidiary chamber, preventing the predators from reaching the brood (Fig. 1b). The diameter of the opening in the wall is fitted to the ergatoid queen’s frontal disk.

Queen
Ergatoid

Nomenclature

 *  conops. Blepharidatta conops Kempf, 1967d: 355, figs. 4, 5 (w.) BRAZIL. See also: Diniz, Brandão & Yamamoto, 1998: 270.

Worker
(holotype). - Total length 4.4 mm; maximum length of head capsule 1.12 mm; maximum width of head (eyes excluded) 0.93 mm; scape length 0.77 mm; maximum diameter of eyes 0.13 mm; Weber's length of thorax 1.23 mm; hind femur length 1.07 mm; petiole length 0.72 mm; petiole width 0.24 mm. Dark reddish brown; legs and gaster chestnut brown. Integument opaque, finely and densely reticulate-punctate throughout, with a silky sheen. Microsculpture of gaster rather superficial, therefore somewhat shining.

Head. Mandibles finely striate; chewing border with 5 teeth, apical and subapical teeth (often worn off) stronger than basal ones, prominent, pointed. Anterior border of clypeus convex; central portion perpendicular, shallowly concave, basal half laterally marginate, the margination ending above in a prominent tubercle or blunt tooth; posterior portion grading into the dorsal face of head with convex and distinct posterior border. Frontal area distinct and impressed. Frontal carinae greatly expanded laterad, covering the sides of head in dorsal view, their lateral border coarsely crenate; just inside the border runs a longitudinal ridge. Dorsum of head with a sagittal impression, broadening caudad and flanked by a pair of diverging, blunt and low ridges, each one sending out laterad two or three very faint transverse ridges. Occiput separated from vertex by an oblique irregular ridge or carina which becomes obsolete in the middle. Occipital corners obliquely truncate, prominent, bearing laterad a blunt excised lobe, mesad a small tooth. Occipital border deeply excised, with a prominent convex lobe in the middle. Antennal scrobe covered by the frontal carinae, deep, attaining the occipital corner, margined below by a carinule running from the occipital corner to above the eye, with another carinule branching off somewhat behind the eye and terminating below it. Cheeks sparsely, coarsely and irregularly rugose, lower border sharply marginate. Gular face and antennal scrobe without macrosculpture, nearly smooth. Eyes conical, unusually prominent, their depth subequal to their width at base. Scape slender, apically gently incrassate, reaching the apex of the scrobe when lodged in it. Funicular segments: I twice as long as broad, II-VII scarcely longer than broad, VIII slightly, IX conspicuously, X strikingly elongate.

Thorax. Pronotum with a prominent scapular and posterior tubercle on each side; a similar tubercle, yet fainter, projecting laterad from mesonotum. Dorsal sutures on thorax absent. Antero-inferior angle of pronotum bidentate. Mesopleura with a prominent, triangular, foliaceous lobe anteriorly, projecting forward, laterad of anterior coxae. Epinotum laterally sharply marginate on base, with very long, thin, acute, scarcely raised and little diverging spines, with a prominent infraspinal lamella marginating the declivous face; this infraspinal lamella bears dorsally another small spine, below it a rounded lobe and at the bottom a rectangular tooth. Dorsum and sides of thorax with heavy, irregular ridges and rugae, lacking on epinotum. Basal and declivous face of epinotum separated from each other by a transverse carinule which is narrowly interrupted in the middle. Legs rather long, sharply and finely punctate; femora only gently incrassate; hind tibiae scarcely longer than tarsite I of the same leg.

Pedicel. Petiole elongate, subcylindrical, anteriorly slightly attenuate both in dorsal and side view. Anteroventrally with a small denticle. Postpetiole in dorsal view subquadrate, scarcely broader than long, its sides straight and subparallel. Both segments irregularly rugose, but less coarsely so than on thorax. Gaster elliptical, narrowly truncated in front.

Pilosity: numerous long, bristly, standing hairs on dorsum of head, thorax, pedicel and gaster; similar hairs, but conspicuously shorter and scarcer on ventral face of petiole, postpetiole and gaster. Fore coxae with a few long standing hairs projecting from the anterior face. Antennae and legs with shorter, rather dense and oblique hairs. Fringing hairs of frontal carinae.

All six specimens are practically alike. The size variation is very little. The holotype is the smallest of the series. The largest specimens measures as follows: Total length 4.6 mm; head length 1.17 mm; head width (without eyes) 0.96 mm; Weber's length of thorax 1.30 mm; petiole length 0.75 mm; petiole width 0.27 mm.

Brandão et al. (2015) - Holotype. HL 1.05; HW 0.88; SL 0.75; ML 0.3; WL 1.2; PL 0.7; Ppl 0.25; Hfl 1; GL 1.05. (n=9): HL 0.9–1.05; HW 0.75–0.9; SL 0.65–0.9; ML 0.25–0.3; WL 0.95–1.2; PL 0.55–0.7; Ppl 0.2–0.3; Hfl 0.75–1.0; GL 0.8–1.05.

Color chestnut to blackish, with contrasting lighter gaster and translucid frontal carina; appendages brownish. Body sculpture varying from areolate-rugose to almost indistinctly foveolate, superposed by irregular rugulae on head, mesosoma, petiole and postpetiole; gaster mostly smooth to weakly areolate near the postpetiolar insertion. Mandible longitudinally striate; central portion of clypeus finely covered by irregular and short transverse striae. Sculpture of scrobe strongly variable, from uniformly areolate to divided into four distinct parts, the anterior one smooth and deeper than the rest; second area with 3–4 transverse curved striae over the areolate rugae, followed by a deep, almost smooth area, and a posterior area of transverse sculpture units, ending with areolate rugulae. Dorsal surface of head ranging from longitudinally areolate-rugose to predominantly smooth and micro-striate at central disc and occipital lobes. Compound eye set within a longitudinal row of polygonal cells formed by rugulae, better seen in lateral view. Mesosoma variably sculptured throughout its entire surface, generally with irregular, vermiculate, longitudinal rugae over the areolate sculpture. Petiole and postpetiole densely areolate and longitudinally rugose in lateral view. Areolate sculpture, when present, concentrated on anterior fifth of gaster, otherwise smooth and shining. Appendages regularly areolate.

In general, body covered by sparse hairs; hairs stiff, long, slightly curved, and uniform in width; some in pairs. Dorsum of mandible with subdecumbent to appressed flexuous short hairs; frontal carina with 12–15 regularly spaced and upwards bent hairs. Dorsum of petiolar node and postpetiole covered by sparse hairs, mostly in pairs, including ventral faces. Anterior face of procoxa with few long and erect hairs. Legs otherwise covered by decumbent short hairs.

Head occipital corner expanded in frontal view. Scape and funiculus almost entirely lodged in the scrobe; frontal carina totally covering the scrobe in frontal view, hiding the antenna and the internal area of scrobe with head in frontal view; compound eye evidently protruding and conical, with about nine 12 facets along its maximum diameter. Ventral surface of head slightly convex, making the anterior region of head wider than rest in lateral view.

Promesonotum slightly convex medially in frontal view, followed by an attenuated curve to lateral margin; dorsal outline of mesosoma convex in profile, with anterior margin angular to evenly rounded; dorsum of promesonotum elevated above level of propodeum; pronotal humeral corner projecting in dorsal view; anteroventral corner pointed; metanotal groove shallow to indistinct in lateral view; dorsal profile of propodeum straight; propodeal spine relatively long and curved upwards, with broad base; infraspinal lamella well-developed and fused to propodeal lobe; propodeal lobe subquadrate in side view, length close to one-third of propodeal spine length.

Pedunculate petiole with a weakly elevated, long and cylindrical node; postpetiole weakly convex dorsally and without ventral processes. Gaster suboval with tergum I anterolaterally feebly angular in dorsal view.

Sting apparatus (Figs 7 A–I). Spiracular plate subquadrate, spiracular external margin separated from posterior plate margin by a distance one and a half times the spiracle internal diameter; ventral tubercle absent. Quadrate plate apodeme area smaller than plate body. Anal plate as in other Blepharidatta species. Oblong plate with long posterior apodeme; subterminal tubercle present. Gonostylus with short membranaceous terminal. Triangular plate dorsal tubercle prominent; median tubercle absent. Lancets as in other Blepharidatta species. Anterolateral processes of sting base with weak anterior tubercle. Sting reduction index 31–41. Furcula dorsal arm length almost equal to side arms´ length; lateral arms narrower at base than dorsal arm.

Queen
Brandão et al. (2015) - (n=2): HL 1.05–1.15; HW 1.35–1.45; SL 0.55–0.65; ML 0.3–0.35; WL 1.25; PL 0.65; Ppl 0.26–0.3; Hfl 0.95; GL 1.35–1.45.

(ergatoid). Larger and drastically distinct from conspecific worker. Surface sculpturing extremely variable, especially on head and anterior slope of pronotum, which can be predominantly smooth and minutely foveolate or densely areolate-rugose. Pilosity denser than in the workers, mainly on mesosomal and metasomal dorsum.

Head and anterior face of pronotum phragmotic; dorsal surface of head rounded, with the frontal carina enormously expanded so that the lateral margins of head, eyes, clypeus and mandibles are totally concealed in frontal view; outline of cephalic disc only interrupted anteriorly by a median emargination, which marks the limits between the frontal lobes. Mesosoma subrectangular and robust. Anterior face of pronotum vertical and rounded dorsally in frontal view, forming with the head a large disc; sides of metanotum sometimes with variably developed wing bud; propodeal spines shorter than those of workers. Gaster well-developed.

Male
Brandão et al. (2015) - (n=2): HL 0.8–0.95; HW 0.55; SL 0.3; ML 0.1–0.15; WL 1.3–1.45; PL 0.6; Ppl 0.25– 0.35; Hfl 1.0–1.11; GL 1.10–1.25.

Body uniformly chestnut to dark-brown, with slightly darker gaster; appendages yellowish. Body entirely areolate with vermiculate longitudinal rugulae over the lateral portions of mesosoma and waist. Gaster smooth and shining. Long, subdecumbent, whitish hairs densely covering the entire body; appendages densely covered by subdecumbent hairs.

Head rounded in frontal view. Mandible short and subfalcate, with vestigial denticles on the masticatory margin; scape very short, not reaching the posterior margin of eye in frontal view; pedicel enlarged and relatively short; first funicular segment about twice as long as the pedicel. Eye huge and extremely protruding, occupying about three-fourths of head in lateral view. Ocelli present and equally developed.

Pronotum vestigial in dorsal view, with almost inconspicuous humeral angles; scutum large, almost straight anteriorly and with a slightly convex posterior margin; notauli weakly impressed. Prescutellum narrow; scutellum wider than long. Metanotal suture well-marked and shallow. Propodeum unarmed, dorsal and posterior margins continuous and gradually inclined posteriorly.

Wings dark amber in color and covered by a dense pubescence; venation reduced; pterostigma elliptical and well-marked; longitudinal veins Sc+R, Rs, M, Cu, and A present; Rs, M, Cu not extending to the external margins of the wing; cells C, R and SR closed. Hind wing with R+Rs and M+Cu veins only; four sub-median hamuli present.

Petiole pedunculate, with weakly elevated, long and cylindrical node; ventral processes absent. Postpetiole subrectangular in dorsal view, longer than broad, and attached to gaster by almost its full width. Gaster elongate, tergite I anterolaterally feebly angular.

Larva
Brandão et al. (2015) - (late instar) (Fig 5 A–E). Body hairs of two main sizes: short (ca. 50–60 microns) sparsely dispersed throughout body, but commoner in the spinulose areas, and long (more than 200 microns) flexuous tapered hairs in a row around pronotum and some around anus, most broken off at base (Fig. 5 E). Eight stouter hairs present on frons (six anteriorly in a row on a fold at mid-length projection and two dorsoposteriorly); clypeal anterior margin with a row of seven minute hairs (circa 3 microns), the central ones even smaller.

Throphorhinium ventral plate with 6 to 7 transverse spinulose striae. Labium with dorsal face forming two blunt low spinulose projections, spinules covering all surfaces but palps. Paxilliform palp with three sensillae. Opening of sericteries not visible in frontal view.

Type Material
6 workers (holotype and paratypes) from Fazenda Retiro de Telhas, Tres Lagoas, Mato Grosso State, Brazil, taken on May 28, 1964 by Karol Lenko, who discovered them at day time walking on the ground in a xerophilous forest of the savanna type callee! locally «cerradao». Holotype and 2 paratypes deposited in the collection of the Departamento de Zoologia, Sao Paulo (DZSP), the remaining paratypes in my private collection (WWK).

Brandão et al. (2015) - Holotype worker: BRAZIL: Mato Grosso do Sul: Três Lagoas, Faz. Retiro das Telhas, 28.v.1964, Exp. Depto Zoologia (Kempf coll. # 4131) (, examined). Paratypes: 3 workers, same data as Holotype (MZSP, examined).