Strumigenys excisa

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Strumigenys excisa
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. excisa
Binomial name
Strumigenys excisa
(Weber, 1934)

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Specimen Labels

Inhabits wet forest leaf litter. The type specimen (from Tuli Creek, near San Miguel, Nicaragua) was in the stomach of a toad, Dendrobates tinctorius, found on the forest floor (Weber 1934, Brown 1953). In Costa Rica, I obtained a series of workers in a Winkler sample of forest floor litter from the Penas Blancas Valley, at 800m elevation. Project ALAS, at La Selva Biological Station, produced a single worker from a Berlese extraction of a soil/litter core (Longino, Ants of Costa Rica). Subsequent sampling has yielded many collections of S. excisa from litter samples in other wet forest locations in Costa Rica.

Identification

Bolton (2000) - A member of the excisa-complex in the Strumigenys excisa-group. Two known species are closely related to excisa, Strumigenys dontopagis and Strumigenys asaphes; characters differentiating the three are compared under the last two names.

Longino (Ants of Costa Rica) - Mandible short and curving downward in profile; lateral head capsule with the antennal scrobe mostly or entirely smooth and shining; propodeal spines present (former Glamyromyrmex); leading edge of scape with long erect setae directed anteriorly or apically, not toward base of scape; disc of postpetiole in dorsal view very broadly U-shaped or V-shaped, with an extremely deeply concave anterior face; spongiform tissue absent from ventral surface of petiole, postpetiole and first gastral sternite; face coarsely rugose over disk, except for narrow median smooth area; face with flexuous setae; setae on face and mesosoma long, abundant, and erect.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Belize, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Strumigenys were once thought to be rare. The development and increased use of litter sampling methods has led to the discovery of a tremendous diversity of species. Many species are specialized predators (e.g. see Strumigenys membranifera and Strumigenys louisianae). Collembola (springtails) and other tiny soil arthropods are typically favored prey. Species with long linear mandibles employ trap-jaws to sieze their stalked prey (see Dacetine trap-jaws). Larvae feed directly on insect prey brought to them by workers. Trophallaxis is rarely practiced. Most species live in the soil, leaf litter, decaying wood or opportunistically move into inhabitable cavities on or under the soil. Colonies are small, typically less than 100 individuals but in some species many hundreds. Moist warm habitats and micro-habitats are preferred. A few better known tramp and otherwise widely ranging species tolerate drier conditions. Foraging is often in the leaf litter and humus. Workers of many species rarely venture above ground or into exposed, open areas. Individuals are typically small, slow moving and cryptic in coloration. When disturbed individuals freeze and remain motionless. Males are not known for a large majority of species.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • excisa. Codiomyrmex excisus Weber, 1934a: 51, fig. 9 (w.) NICARAGUA. Combination in Borgmeierita: Brown, 1953g: 23; in Glamyromyrmex: Brandão, 1991: 344; in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 119. See also: Bolton, 2000: 173.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Bolton (2000) - TL 2.2-2.3, HL 0.55-0.60, HW 0.47-0.50, CI 80-85, ML 0.11-0.13, MI 18-22, SL 0.23-0.26, SI 51-54, PW 0.28-0.31, AL 0.57-0.62 (6 measured).

Clypeus glassy smooth, with widely spaced minute punctures from which hairs arise. Behind the clypeus the cephalic dorsum finely longitudinally rugulose, most densely so away from the midline on the occipital lobes. Sides of alitrunk and propodeal declivity are smooth and shining, but dorsum of alitrunk has fine longitudinal rugular sculpture. Dorsum of petiole node has some fine disorganised short rugulae but disc of postpetiole is smooth. Basigastral costulae are feebly developed on each side of a median gap where the cuticle of the tergite is smooth. Spaces between basigastral costulae contain faint superficial shagreening. Dorsum of clypeus with suberect fine straight simple hairs. Cephalic dorsum with abundant standing simple pilosity. Dorsolateral margins of head in full-face view with abundant freely projecting fine hairs, some of which are long and subflagellate to flagellate. Scapes with scattered proj ecting hairs on the leading edge. Dorsal surfaces of club segments of antennae with long stiff suberect simple hairs that are at least as long as the maximum thickness of the segments. Dorsal alitrunk with abundant long fine simple hairs; pronotal humeral hair similar to other hairs but longer and subflagellate. Dorsal (outer) surfaces of hind tibiae and basitarsi with numerous long fine standing hairs that are distinctly longer than the segments from which they arise. Dorsa of waist segments and gaster clothed with abundant soft curved to flexuous standing hairs.

Type Material

Holotype worker, NICARAGUA: San Mejuel , Tuli Creek, xi.1916, from stomach of tree toad Dendrobates tinetorum, no. 2821-3433 (G. H. Noble) (Museum of Comparative Zoology) (parts card-pointed, other parts on microscope slide) [examined].

References