Monomorium ebeninum

In Central America and the Caribbean Islands this is one of the most common ants found in coastal areas. Wetterer (2017) collected this species on many islands in the Lesser Antilles "through vegetation beating in open areas. Large M. ebeninum colonies often nest in dead branches."

Identification
DuBois (1986) - Since Monomorium ebeninum is the only species with wingless queens that occurs in the Caribbean region, it should not be confused with any other species. Three other species occur in areas which border the range of M. ebeninum: Monomorium cyaneum, Monomorium trageri, and Monomorium viridum. Queens of M. ebeninum are separated from those of these other species since the profile of the scutum and scutellum of M. ebeninum queens is flat or slightly concave while the profile of the remaining species is clearly convex. Additionally, the head sculpturing in M. ebeninum is quite reduced. Workers of M. ebeninum can be separated from the other species since their propodeum has basal and declivitous faces of approximately equal length. Although this is also true of M. cyaneum workers, the mesopleuron in M. ebeninum workers is smooth and shining, while it is punctuate in M. cyaneum workers.

Distribution
This species is found in Central America, the Caribbean Islands (including the Bahamas), and southern Florida. It has been collected from many of the islands and from Atlantic and Pacific coastlines in many parts of Central America (DuBois 1986). It has been found a few times in the Florida Keys, where it was claimed to have been introduced (Deyrup, Davis & Cover, 2000) but Wetterer (2017) has shown that this species is likely native to this area.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Barbados, Costa Rica, Cuba, Dominican Republic, Greater Antilles, Grenada, Guadeloupe, Guatemala, Haiti, Honduras, Lesser Antilles, Mexico, Puerto Rico, Trinidad and Tobago.



Biology
DuBois (1986) - This species presumably nests under stones and in plant cavities. Forel (1899) indicated that M. ebeninum lives in stems and hollow branches. Wheeler (1905a) recorded it from under stones, in cavities of Tillandsia spp., and in dry twigs of buttonwood bushes. Smith (1936b: 832) elaborated further: "This is one of the most common ants of the West Indies... It forms populous colonies which are characterized by having many reproductive queens to a colony. Their great adaptability is indicated by the fact that this species nests in both soil and wood, back of the leaf sheaths or [sic] corn and bananas, in cabbage heads, Tillandsias, and in the fruits of Hibiscus sabdariffa. The workers are exceedingly fond of honeydew. They have been noted attending such insects as Saissetia hemispherica Targ., Coccus viridus Green, the aphid Sipha flava Forbes, etc. The ants are also highly predacious." Wolcott and Martorell (1937) recorded this ant as a predator on the eggs of the sugarcane moth borer, Diatraea saccharalis Fabricius (Lepidoptera: Pyralidae). Although Lavigne (1977) recorded this species from lawns in Puerto Rico, he provided no details on the nest's microhabitat nor structure. Wheeler (1905a) recorded multiple queens per nest (up to 12). Although M. ebeninum has a moderately broad altitudinal tolerance (0-1600 m above sea level), it is most frequently collected in coastal areas. Sexual forms are produced in spring {collections of males: Jamaica: Montego Bay, March 14, 1911; Andros Island (Bahama Islands): Mangrove Cay, May 31, 1904}.

Wolcott (1948) mentions this ant is eaten by the lizards Anolis stratulus and A. cristatellus. Lavigne (1977) collected workers from stomachs of the following two frog species: Eleutherodactylus cochranae and E. coqui.

Puerto Rico
Wheeler (1908): Common under stones, in Tillandsias and under bark. A number of females taken from a single nest at Arecibo are wingless and subergatoid like those I have described from the Bahamas.

Florida
Found a few times in the Florida Keys. Nests may be in the ground or in dead branches or in bromeliads. It is an aggressive scavenger, but does not seem to invade houses in the Bahamas, where it is much commoner than in Florida. Pest status: none. First published Florida record: Deyrup et al. 1988; earlier specimens: 1986. (Deyrup, Davis & Cover, 2000.)

Nomenclature

 *  ebeninum. Monomorium minutum r. ebeninum Forel, 1891b: 165 (in text) (w.) ANTILLES. Forel, 1893g: 388 (q.); Forel, 1897b: 300 (m.); Wheeler, W.M. 1905b: 88 (q.m.). Subspecies of carbonarium: Wheeler, W.M. 1905b: 88; Forel, 1912g: 3; Mann, 1922: 29; Wheeler, W.M. 1942: 198. Raised to species: Forel, 1913l: 218; DuBois, 1986: 103.

DuBois (1986) - Queen: Wingless; petiole and postpetiole as in Figures 119, 121, and 122; scutum and scutellum slightly depressed dorsally or flat; metanotum projecting to level of propodeum and scutellum; propodeum angular. Male: Genitalia and sterna as in Figures 125, 128-131. Worker: Propodeum angular; mesopleuron not punctate; petiole as in Figure 121; PI 40-44 (41).

Worker
DuBois (1986) - Head: Measurements (representing different localities; N= 10) HL 0.48-0.55 (0.51), HW 0.38-0.42 (0.40), SL 0.35-0.40 (0.39), EL 0.07-0.09 (0.08), MOD 0.05-0.06 (0.05). Structure - CI 76-84 (78), SIL 67-95 (78), SIW 71-105 (95). Side of head straight. Clypeal teeth short, blunt. Sculpture - Several small, short, parallel, longitudinal rugae on clypeus; several small, short, parallel, longitudinal rugae beginning all along lateral margin of clypeus, continuing to antennal insertion. Alitrunk: Measurements PW 0.25-0.28 (0.26), PL 0.21-0.25 (0.23), WL 0.52-0.62 (0.56). Structure - Propodeum angular, both faces of approximately equal length. PI 40-44 (41). Petiole: As in Figure 124. Dorsum of node flat to slightly emarginate. Setae erect to suberect on dorsum of node, absent elsewhere. Postpetiole: As in Figure 124. Dorsum of node flat to slightly emarginate. Gaster: Setae of first gastral tergite reaching or exceeding level of dorsum of postpetiolar node. Color: Head dark brown to brown except as follows: mandibles yellow-brown to brown. Alitrunk and legs dark brown to brown. Gaster dark brown.

Queen
DuBois (1986) - Head: Measurements (representing different localities; N= 10) HL 0.65-0.72 (0.68) {0.72}, HW 0.55-0.65 (0.60) {0.61}, SL 0.42-0.52 (0.49) {0.52}, IOD 0.10-0.17 (0.14) {0.12}, OD 0.04-0.07 (0.05) {0.05}, EL 0.15-0.18 (0.16) {0.18}, MOD 0.10-0.13 (0.12) {0.13}. Structure - CI 80-93 (88) {85}, SIL 62-77 (72) {72}, SIW 76-88 (82) {85}. Side of head straight. Scape not reaching occiput. Masticatory margin of mandible with 4 >rarely 5< teeth. Clypeal teeth moderately sharp to blunt, short. Frontal carinae diverging strongly posteriorly. Sculpture - Moderate, parallel, longitudinal rugae beginning all along lateral margin of clypeus, continuing to level of middle of compound eye after converging slightly near frontal carinae >rugae above frontal carinae may be absent or greatly reduced< (Fig. 120). Alitrunk: Measurements PW 0.40-0.52 (0.42) {0.43}, PL 0.23-0.32 (0.29) {0.23}, WL 1.05-1.18 (1.11) {1.13}. Structure - Scutum and scutellum slightly depressed dorsally. Mesopleural suture deflected ventrally at posterior end (with small pit on anterior end and larger pit on posterior end). Propodeum angular, basal and declivitous faces of approximately equal length. PI 20-30 (26) {20}. Wings absent (fusion of sclerites indicate queens are wingless). Sculpture - Entire propodeum covered with small, non-piliferous punctures (leading to a granular appearance); declivitous surface of propodeum with moderate, parallel, transverse rugae. Petiole: As in Figures 119 and 121. Dorsum of node flat to slightly emarginate. Setae decumbent to appressed on anterior surface of node, subdecumbent to decumbent on dorsum, absent elsewhere. Entire petiole smooth and shining (with small, piliferous punctures on anterior surface and dorsum) except as follows: posterior 1/5 of petiole with moderate, concentric, semicircular, transverse rugae. Postpetiole: As in Figures 119 and 122. Dorsum of node flat. Setae subdecumbent to decumbent on posterior surface of node, absent elsewhere. Postpetiolar surface smooth and shining except as follows: posterior 1/2 with dense, moderate, non-piliferous punctures. Color: Entire body and appendages usually brown to dark brown. All setae white.

Male
DuBois (1986) - Head: Measurements (representing different localities; N= 3) HL 0.55-0.61 (0.59), HW 0.61-0.68 (0.64), SL 0.24-0.28 (0.26), IOD 0.18-0.20 (0.19),OD 0.06-0.08 (0.07), EL 0.22-0.25 (0.24), MOD 0.12-0.18 (0.16). Structure - CI 100-113 (109), SIL 39-47 (44), SIW 39-41 (40). Maxillary palp 1 - segmented (Fig. 127); labial palp 1 segmented (Fig. 126). Clypeal teeth absent. Frontal carinae not diverging posteriorly. Pilosity - Setae erect near clypeus, mandible, and occiput, decumbent to appressed elswhere. Sculpture - Several moderate to large, parallel, longitudinal rugae beginning all along lateral margin of clypeus, extending to antennal insertion. Several small to moderate, parallel, longitudinal rugae extending from clypeus to level of frontal carinae. Additionally, several moderate, concentric, semicircular rugae extending from level of compound eye to occiput and following contour of occiput. Alitrunk: Measurements PW 0.50-0.60 (0.56), PL 0.30-0.36 (0.32), WL 1.12-1.27 (1.20). Structure - Pronotal-scutal suture on dorsal 1/2 of alitrunk. Mesopleural suture as in queen except as follows: pit absent on anterior end. Metanotum (in lateral view) not projecting to level of propodeum and scutellum. Propodeum angular, basal face 2 times as long as declivitous face. PI 25-28 (27). Sculpture - Several moderate, semicircular, concentric rugae with vertex at anterior edge of pronotum, extending posteriorly (as parallel, longitudinal rugae) to scutum; sculpturing of sutures as in Figure 125. Petiole: As in Figure 125. Setae appressed on anterior surface of node, erect to suberect on dorsum, absent elsewhere. Entire surface of node, erect to suberect on dorsum, absent elsewhere. Entire surface smooth and shining. Postpetiole: As in Figure 125. Setae decumbent to subdecumbent on anterior surface of node, erect to suberect on posterior surface of node and venter, absent elsewhere. All surfaces smooth and shining. Gaster: Setae of first gastral tergite reaching or exceeding level of dorsum of postpetiolar node. Genitalia: As in Figures 125 and 128-131. Eighth sternite with emargination approximately 1/2 as deep as wide (Fig. 128). Ninth sternite with 8 erect setae (Fig. 129). Aedeagus with 8 teeth; toothed margin straight (Fig. 131). Volsella with reduced digitus; lacking cuspis (Fig. 130). Color: Head and antenna brown to dark brown except as follows: mandible yellow to yellow-brown. Alitrunk brown to dark brown, legs yellow to yellow-brown. Petiole and postpetiole brown to yellow-brown, gaster brown to dark brown. Genitalia brown to yellow-brown. All setae white to yellow.

Type Material
DuBois (1986) - Syntypic series consisting of 2 queens, 1 male, and 16 workers from the following localities: Grenada (male), St. Vincent (queens), St. Thomas (Antille) (workers). Six workers bear the date 14 X 78. Lectotype queen here designated from MHNG series bears red, handwritten label: Monomorium/ ebeninum/ Forel/ Lectotype/ M. DuBois 1983/. It is from St. Vincent.

Forel (1891: 165) described the distinguishing characters of this species: "La race de l'Amérique tropicale que j'avais cru devoir rapporter au carbonarium (Ameisen der Antille St. Thomas, 1881) et que j'ai recue dés lors du Guatémala, etc., se distingue nettement par les deux élévations du métanotum, par sa large échancrure méso-métanotale, par la face déclive plus haute du métanotum plus éléve qui forme presque un angle avec la face basal, par le premier noeud du pédicule plus mince et plus longuement pétiolé. Je propose de l'appeler ebeninum." Presumably, the material from Guatemala was provided through Pergande (W. L . Brown, Jr., pers. comm.); however, none of this material can be discovered in the remains of Pergande's collection. The remainder of this type series is in Geneva (MHNG). A few of these specimens are clearly labelled "TYPUS"; these include the male, both queens, and 6 workers. I assume that Forel regarded these specimens as part of his type series and merely chose to list their localities as "etc." when he described M. ebeninum. I chose the lectotype, designated above, in an effort to restrict the type locality and to reduce future confusion since queens are easier to identify than workers.