Pheidole biconstricta

P. biconstricta is a conspicuous ant in much of the tropical forests of the New World. It forms large colonies, with populations possibly in the tens of thousands, that nest in rotting logs and stumps on the forest floor. John T. Longino (1997) reports that in Costa Rica, “Workers are aggressive, and forage day or night. Large numbers of minor and major workers may be observed swarming out from nests and retrieving live insect prey, with a behavior reminiscent of army ants. Workers also tend Homoptera, and visit extrafloral nectar sources. Colonies may build scattered carton shelters on low vegetation, and tend membracids and other Homoptera beneath them. Workers may aggressively defend extrafloral nectar sources (e.g. Passiflora shoots), driving away herbivores and other ants. Colonies use carton construction to form baffles in rotten wood, and galleries running up tree trunks. At Rara Avis, workers were observed tending large riodinid larvae under carton galleries. Founding queens are found under loose bark of dead wood, in dead branches, and very commonly under epiphyte mats on recently fallen trees.” (Wilson 2003)

Identification
See the description in the nomenclature section.

Distribution
Widespread and locally abundant, occurring mostly in tropical moist forests from Guatemala to Brazil and Bolivia; present in Trinidad but absent from Tobago and the rest of the West Indies. Ranges to at least 1500 m in Costa Rica and to 2500 m in Colombia. (Wilson 2003)

This taxon was described from Colombia.

Biology
Charles Kugler (1979d) has described the capture of live insect prey by “gang-pulling, and the hypertrophial pygidial glands, which secrete a viscous gumming agent and irritant when smeared on enemies. Another behavior unusual for Pheidole is the lifting of the gaster toward the enemy, making release of the toxin material more effective. Alarm pheromones also emanate from the same gland.”

Description
From Wilson (2003): I have examined the types of all the biconstricta related forms (Pheidole biconstricta Mayr 1870a: 399. Syn.: Pheidole biconstricta subsp. bicolor Emery 1890c: 50, n. syn.; Pheidole biconstricta r. rubicunda Emery 1890c: 50, n. syn.; Pheidole biconstricta rubicunda var. fuscata Emery 1890c: 51 (unavailable name, quadrinomial); Pheidole biconstricta subsp. hybrida Emery 1894d: 154, n. syn.; Pheidole radoszkowskii r. lallemandi Forel 1901d: 133, n. syn.; Pheidole biconstricta bicolor var. regina Forel 1908c: 52, n. syn.; Pheidole biconstricta hybrida var. angustella Forel 1912g: 222 (unavailable name, quadrinomial); Pheidole biconstricta var. surda Forel 1912g: 222, n. syn; Pheidole biconstricta subsp. burtoni Mann 1916: 436, n. syn. (provisional); Pheidole holmgreni Wheeler 1925a: 18, n. syn.; Pheidole holmgreni festata Wheeler 1925a: 20, n. syn.).

What I have regarded here as the single species biconstricta is highly variable in details of size, sculpturing, and color, both locally and geographically, with general and overlapping intergradation. Closer studies with more material may well reveal biconstricta to be a complex of sibling species, to which at least some of the names will apply, but for the time being I have chosen the more conservative arrangement, that is, recognition of a single, very variable species.

A member of the biconstricta group distinguished as follows.

Major: large, with well-developed propodeal spines and prominent rounded humeral angles; head dorsal surface foveolate, space between eye and antennal fossa rugoreticulate; first 2 gastral tergites mostly shagreened and opaque; pilosity sparse on head, moderate on rest of body; body color reddish yellow (“orange”) to dark reddish brown, usually a lighter shade; one variant (bicolor, possibly a distinct species) has a contrasting paler gaster.

Minor: head conspicuously narrowed, with nuchal collar; mesonotal convexity well-developed, leaning forward; propodeal spines short, thick, and erect; occiput, mesothorax, and propodeum foveolate and opaque; anterior half of first gastral tergite shagreened and opaque.

MEASUREMENTS (mm) Lectotype major: HW 1.62, HL 1.70, SL 1.08, EL 0.22, PW 0.82. Paralectotype minor: HW 0.78, HL 0.94, SL 1.12, EL 0.16, PW 0.54.

COLOR Major: yellowish brown (possibly faded).

Minor: light reddish brown; otherwise, see Diagnosis above.



'''Figure. Upper: lectotype, major (with 2 hypostomal teeth; a 4-toothed variant is also shown). Lower: paralectotype, minor. Scale bars = 1 mm.'''

Type Material
- as reported in Wilson (2003)

Type Locality Information
COLOMBIA: Bogotá. (Wilson 2003)

Etymology
L biconstricta, constricted (pinched) twice, once in front of the mesonotum and once behind it. (Wilson 2003)

Additional References
Kugler, C. 1979d. Alarm and defense: a function for the pygidial gland of the myrmicine ant, Pheidole biconstricta. Ann. Entomol. Soc. Am. 72: 532–536

Mayr, G. 1870a. Formicidae novogranadenses. Sitzungsber. Kais. Akad. Wiss. Wien Math.-Naturwiss. Cl. Abt. I 61: 370–417

Text and images from this publication used by permission of the author.