Strumigenys membranifera

This ant has been spread around the world via human commerce.

Identification
See the description below.

Distribution
Bolton (2000) - P. membranifera is mainly a pantropical tramp species, but it also occurs outside the tropics in favourable locations. Material examined subsequent to that listed in Bolton (1983) is from Sierra Leone, Egypt and U.S.A.. Type-data of the various synonyms record the species from Italy, Tunisia, St Thomas I. in the West Indies, Fiji Is, China, U.S.A. and Hawaii. Wilson & Taylor (1967) note its presence in Samoa. Kempf (1972) has Neotropical records from Puerto Rico, Costa Rica and Venezuela. In the U.S.A. membranifera has been recorded from Alabama, California, Florida, Georgia, Louisiana, Mississippi and Texas (M.R. Smith, 1931; D.R. Smith, 1979; Deyrup, Johnson, et al., 1989; Cokendolpher, 1990). Deyrup (1997) records it from Bahamas.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Comoros, Sierra Leone, South Africa. Australasian Region: Australia. Indo-Australian Region: Fiji, Guam, Hawaii, Indonesia, Marshall Islands, Micronesia (Federated States of), New Guinea, Northern Mariana Islands, Samoa, Solomon Islands, Tonga, Wallis and Futuna Islands. Malagasy Region: Mayotte, Seychelles. Nearctic Region: United States. Neotropical Region: Barbados, British Virgin Islands, Cuba, Dominican Republic, Ecuador, Galapagos Islands, Greater Antilles, Mexico, Puerto Rico, Turks and Caicos Islands. Oriental Region: Bhutan, India, Nepal, Taiwan. Palaearctic Region: Balearic Islands, China, Egypt, Greece, Iberian Peninsula, Israel, Italy, Japan, Malta, Spain, Tunisia.



Habitat
From moist forests to disturbed open areas, such as lawns and pastures.

Biology
Wilson (1954) studied two colonies in laboratory nests over an eight-month period. He reported this species accepted a wide range of small invertebrates. The following is a modified synopsis of additional observations:

These ants are the most active of the dacetines studied and show unexpected pugnacity under certain conditions. Japyx and termites were frequently attacked in the artificial nests with a viciousness approaching that of some of the more aggressive larger myrmicines. The little dacetines actually rushed at these insects when they contacted them, seizing hairs or appendages and doubling up in an effort to sting.

Although they lacked long mandibles to be used as a weapon of shock, they were able to panic fairly large individuals and dispose of them as quickly as dacetines with long mandibles. Since insects combated in this fashion were rarely eaten, it is assumed that such aggressive behavior is used in the defense of the nest.

Stalking of Collembola is in an entirely different mood and is usually executed cautiously and with deliberation. Workers rarely recognize an insect until they come in contact with it, but are very sensitive to nearby movement and probably depend a great deal on this in spotting prey.

As soon as the worker becomes aware of the presence of a collembolan, it "freezes" in a lowered, crouching position and holds this stance briefly. If the collembolan is to its back or side, the worker now turns very slowly to face it. Once it is aligned with the collembolan, it begins a forward movement so extraordinarily slow that it can be detected only by persistent and careful observation. Several minutes may pass before the ant finally maneuvers over less than a millimeter's distance to come into a striking position, and it may be remain in this position for as much as a minute or more. During this time the collembolan may move away for one reason or another, in which case the ant rarely attempts to follow but begins to forage anew. Workers open their mandibles only to about a 60° angle. Tactile labral hairs are present and eventually come to touch the prey. The mandibular strike is sudden but lacking a long mandible it is usually directed at an appendage and does not have the same stunning effect on the collembolan. Captured insects often struggle vigorously to escape, but the ants are very tenacious and retain a fast grip until they are able to sting their prey into immobility.

Unusual behavior in foraging workers was sometimes observed. Occasional bold workers were seen to approach their prey rapidly and attempt to seize a hair or appendage, and these were frequently successful. Sometimes workers would "freeze" when Collembola were moving rapidly around them and wait without moving, apparently in anticipation of ambushing the animals as these blundered into their mandibles.

Workers were never observed to participate in any sort of trophallaxis, either between workers or between workers and larvae.

Development times (constant temperature of 27 C) in days were found to be: egg-13, larvae-19 and pupa-19

This species is relatively adaptable in its nesting requirements being found in many different situations that vary from forest litter to under bits of slate in a cultivated field. Its moisture requirements are not as strict as for many congeners, and membranifera venture into relatively dry, open soil.

Nomenclature

 *  membranifera. Strumigenys (Trichoscapa) membranifera Emery, 1869b: 24, fig. 11 (w.) ITALY. Emery, 1916b: 205 (q.); Wheeler, G.C. & Wheeler, J. 1991b: 93 (l.). Combination in S. (Cephaloxys): Emery, 1916b: 205; in Trichoscapa: Brown, 1948e: 113; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 123. Senior synonym of foochowensis, marioni, santschii, silvestriana, simillima, vitiensis, williamsi: Brown, 1948e: 114. See also: Brown, 1949d: 6; Wilson, 1954: 483; Bolton, 1983: 319; Bolton, 2000: 322.
 * simillima. Strumigenys membranifera r. simillima Emery, 1890b: 69, pl. 8, fig. 5 (w.) ANTILLES. Combination in S. (Cephaloxys): Emery, 1924d: 325. Junior synonym of membranifera: Brown, 1948e: 114.
 * santschii. Strumigenys membranifera var. santschii Forel, 1904c: 6 (w.) TUNISIA. Junior synonym of membranifera: Brown, 1948e: 114.
 * vitiensis. Strumigenys (Cephaloxys) vitiensis Mann, 1921: 461, fig. 22 (w.) FIJI IS. Junior synonym of membranifera: Brown, 1948e: 114.
 * foochowensis. Strumigenys (Cephaloxys) foochowensis Wheeler, W.M. 1928c: 28 (q.) CHINA. Junior synonym of membranifera: Brown, 1948e: 114.
 * silvestriana. Strumigenys (Cephaloxys) silvestriana Wheeler, W.M. 1928c: 27 (w.) CHINA. Junior synonym of membranifera: Brown, 1948e: 114.
 * marioni. Strumigenys (Cephaloxys) membranifera var. marioni Wheeler, W.M. 1933h: 276 (w.) U.S.A. Junior synonym of membranifera: Brown, 1948e: 114.
 * williamsi. Strumigenys (Cephaloxys) membranifera var. williamsi Wheeler, W.M. 1933h: 276 (w.q.) HAWAII. Junior synonym of membranifera: Brown, 1948e: 114.

Bolton (2000) - The single species of this group previously constituted the genus Trichoscapa in the sense of Brown (1948b) and Bolton (1983), now abandoned (Bolton, 1999).

Worker
Bolton (2000) - TL 1.9 - 2.1, HL 0.46 - 0.50, HW 0.40 - 0.44, CI 84 - 90, ML 0.08 - 0.10, MI 16 - 20, SL 0.22 - 0.24, SI 51 - 57, PW 0.23 - 0.26, AL 0.50 - 0.53 (10 measured; from Bolton, 1983). As there is only one species in the group its diagnosis will also serve to characterise the species.

Mandibles in full-face view and at full closure short triangular, serially dentate and the masticatory margins engaging throughout their length. Dorsal surface of mandible sharply depressed immediately behind the level of the basal tooth, the rim of the depression appearing as a sharp transverse edge that traverses the width of the mandible immediately behind the level of the basal tooth, and paralleling the anterior clypeal margin. The transverse edge appears to be followed proximally by a deep transverse groove or impression immediately in front of the anterior clypeal margin. In profile dorsal surface of mandible arched-downcurved from clypeal margin to apex. In ventral view outer margin of mandible with a shallowly rounded prebasal inflected angle. MI 16 - 20.

Dentition. Basally with a dental row of 7 sharply triangular teeth of which 1 - 5 are slightly taller than 6 - 7, followed distally by 4 minute denticles and a slightly enlarged apical tooth, giving a total dental count of 12.

Basal lamella of mandible truncated-triangular, not in the same plane as the principal basal dental series but located below and slightly behind the basal tooth; not visible in full-face view with the mandibles closed.

Labrum terminates in a pair of narrow elongate triangular lobes.

Clypeus with anterior margin broad, transverse to extremely shallowly convex. Lateral margins of clypeus approximately straight and more or less parallel. Anterolateral clypeal angles located much further laterally than the point at which the outer margins of the mandibles intersect the anterior clypeal margin.

Clypeal margins and dorsum with minute appressed pubescence only, appearing naked under normal magnifications. In ventral view the lateral clypeal margins extending well beyond the outer margins of the fully closed mandibles through the basal third or more of their length.

Preocular carina visible anteriorly in full-face view but behind level of frontal lobes concealed from view by frontal carina.

Ventrolateral margin of head between eye and mandible marginate, the margination curving shallowly upward anteriorly from the eye; not terminating anteriorly in a tooth. Postbuccal impression small and inconspicuous.

Cuticle of side of head within scrobe finely shagreenate or punctulate.

Scape short, SI 51 - 57, dorsoventrally flattened, the dorsum and ventre converging anteriorly so that the leading edge is a sharp flange or even a thin lamella. Ventral surface of scape behind the leading edge concave.

Leading edge of scape with a row of large spatulate hairs, one or more of which are curved toward the base of the scape.

Pronotum sharply marginate laterally, without a median longitudinal carina.

Propodeum with a broad lamella running down the declivity; lamella incorporating the propodeal teeth which are indistinguishable except for a minute apical point.

Spongiform appendages massively developed on waist segments. Base of first gastral stemite in profile with a distinct pad of dense spongiform tissue.

Pilosity. Pronotal humeri without projecting hairs of any description. A single pair of feebly clavate hairs present at highest point of vertex, otherwise dorsolateral and dorsal surfaces of head without standing pilosity; apicoscrobal hair absent. Dorsal surfaces of alitrunk, waist segments and first gastral tergite without standing pilosity. Ground-pilosity of head minute, sparse and appressed, very inconspicuous.

Sculpture. Dorsum of head behind clypeus finely reticulate-punctate. Dorsum and sides of alitrunk mostly to entirely smooth and shining; disc of postpetiole smooth.

Type Material
Bolton (2000):

Holotype worker, ITALY: Napoli, Portici [examined].

Strumigenys membranifera r. simillima Emery, 1890: 69, pl. 8, fig. 5. Holotype worker, ANTILLES IS: St Thomas I. (MCSN) [not seen].

Strumigenys membranifera var. santschii Forel, 1904b: 6. Syntype workers, TUNISIA: Kairouan (F. Santschi) [examined].

Strumigenys (Cephaloxys) vitiensis Mann, 1921: 461, fig. 22. Syntype workers, FIJI IS: Vanua Levu, Lasema (W'M. Mann) [examined].

Strumigenys (Cephaloxys) silvestriana W.M. Wheeler, 1928a: 27. Syntype workers, MACAO: (F. Silvestri) (MCZ) [examined].

Strumigenys (Cephaloxys) foochowensis W.M. Wheeler, 1928a: 28. Holotype queen, CHINA: Foochow (F. Silvestri) (location of holotype unknown, not in MCZ, presumed lost).

Strumigenys (Cephaloxys) membranifera var. marioni W.M. Wheeler, 1933: 276. Syntype workers, U.S.A.: Mississippi (M.R. Smith) (MCZ) [examined].

Strumigenys (Cephaloxys) membranifera var. williamsi W.M. Wheeler, 1933 : 276. Syntype workers, HAWAII: S of Olaa, off the road to Puna, iv.1932, under moss etc. (F. X. Williams) (MCZ) [examined].