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Throughout the mainland Neotropics, from Guatemala to Brazil and Bolivia. In Costa Rica: throughout the country in wet forest areas, to 1500m elevation in Monteverde.
Founding queens are found under loose bark of dead wood, in dead branches, and very commonly under epiphyte mats on recently fallen trees.
In Penas Blancas, Longino observed an interaction with phorid flies. Workers were streaming up a tree trunk. Phorids were hovering above. One landed on the head of a soldier. Afterwards, workers grabbed the soldier by the legs and slowly began to drag it down the trunk.
biconstricta is a complex lineage with many infraspecific taxa in the taxonomic literature. Four of these have type localities in Costa Rica:
biconstricta surda Forel 1912:222
biconstricta bicolor Emery 1890:50
biconstricta bicolor regina (unavailable quadrinomial)
biconstricta rubicunda Emery 1890:50
Wilson (2003) synonymized them all under biconstricta.
In Costa Rica, specimens from the southern Pacific lowlands are light orange. In Monteverde, they are two-toned, with light orange head and mesosoma, and somewhat darker gaster. On the Atlantic slope they are brown to dark brown. The transition can be sharp: specimens of the two-toned Monteverde form are known from open areas in and around Monteverde, on the Pacific slope west of the cloud forest that covers the continental divide; the dark brown form is common in the Penas Blancas Valley, about 5km east of Monteverde on the Atlantic slope. There is also variation in sculpture, but it does not show geographic patterns and varies within populations.
Original images of above color forms: Manuel Antonio, Monteverde, Penas Blancas, La Selva.
Kugler, C. 1979. Alarm and defense: a function for the pygidial gland of the myrmicine ant, Pheidole biconstricta. Annals of the Entomological Society of America 72:532-536.
Wilson, E. O. 2003. Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus. Harvard University Press, Cambridge, Mass
Pheidole biconstricta MayrHNS 1870a: 399. Syn.: Pheidole biconstricta subsp. bicolor EmeryHNS 1890c: 50, n. syn. ; Pheidole biconstricta r. rubicunda EmeryHNS 1890c: 50, n. syn. ; Pheidole biconstricta rubicunda var. fuscata EmeryHNS 1890c: 51 (unavailable name, quadrinomial); Pheidole biconstricta subsp. hybrida EmeryHNS 1894d: 154, n. syn. ; Pheidole radoszkowskii r. lallemandiHNS Forel 1901d: 133, n. syn. ; Pheidole biconstricta bicolor var. reginaHNS Forel 1908c: 52, n. syn. ; biconstricta hybrida var. angustellaHNS Forel 1912g: 222 (unavailable name, quadrinomial); Pheidole biconstricta var. surdaHNS Forel 1912g: 222, n. syn; Pheidole biconstricta subsp. burtoni MannHNS 1916: 436, n. syn. (provisional); Pheidole holmgreni WheelerHNS 1925a: 18, n. syn. ; Pheidole holmgreni festata WheelerHNS 1925a: 20, n. syn.
I have examined the types of all the above listed forms that are available nomenclaturally. What I have regarded here as the single species biconstrictaHNS 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 biconstrictaHNS 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.
types Naturhist. Mus. Wien.
Etymology L biconstrictaHNS, constricted (pinched) twice, once in front of the mesonotum and once behind it. Diagnosis A member of the biconstrictaHNS 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 (" bicolorHNS," 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.
Range 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.
Biology P. biconstrictaHNS 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."
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 PheidoleHNS 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."
Figure Upper: lectotype, major (with 2 hypostomal teeth; a 4-toothed variant is also shown). Lower: paralectotype, minor. COLOMBIA: Bogota. Scale bars = 1 mm.
Found most commonly in these habitats: 42 times found in tropical wet forest, 14 times found in montane wet forest, 29 times found in wet forest, 20 times found in rainforest, 20 times found in cloud forest, 22 times found in 2º wet forest, 14 times found in montane rainforest, 12 times found in mesophil forest, 15 times found in ridgetop cloud forest, 17 times found in oak cloud forest, ...
Found most commonly in these microhabitats: 112 times at bait, 56 times ex sifted leaf litter, 22 times beating vegetation, 2 times in clearing, 8 times on low vegetation, 5 times foragers, 4 times ground foragers, 7 times beating veg., 7 times ground forager, 5 times under epiphytes, 4 times nest in dead wood, ...
Collected most commonly using these methods: 86 times search, 100 times Baiting, 31 times Beating, 29 times MiniWinkler, 18 times MaxiWinkler, 17 times bait, 16 times Winkler, 4 times Sweeping, 3 times Malaise, 3 times beating low vegetation, 3 times hand collected, ...
Elevations: collected from 5 - 1940 meters, 799 meters average
Collect Date Range: collected between 1938-12-10 00:00:00.0 and 2022-01-17 00:00:00.0
Type specimens: Lectotype of Pheidole biconstricta: casent0916051; Lectotype Pheidole inermis: casent0601290; Not Provided: casent0283253; Paralectotype Pheidole inermis: casent0601291; paratype Pheidole xanthogaster: jtlc000016577; syntype of Pheidole biconstricta: casent0919768, casent0919769; syntype of Pheidole biconstricta surda: casent0901477; syntype of Pheidole biconstricta bicolor: casent0904353, casent0904354; syntype of Pheidole biconstricta hybrida: casent0904355, casent0904356; syntype of Pheidole biconstricta rubicunda: casent0904350, casent0904351; syntype of Pheidole biconstricta surda: jtlc000014066, jtlc000014067; syntype of Pheidole radoszkowskii lallemandi: casent0908089, casent0908090; type of Pheidole biconstricta hybrida: focol1426, focol1427; Type of unavailable quadrinomial: Pheidole biconstricta bicolor regina: casent0908085, casent0908086; Type of unavailable quadrinomial: Pheidole biconstricta hybrida angustella: casent0908087, casent0908088; Type of unavailable quadrinomial: Pheidole biconstricta rubicunda fuscata: casent0904352