Liometopum

Most species of Liometopum occur in drier forested areas and they are often associated with oak or pine. These ants form large, arboreal nests and forage epigeically in columns. (However, one North American species, Liometopum apiculatum, is apparently primarily a ground nester.) The nest chambers are often located in inaccessible regions of tree boles and are difficult to collect. In the field, these ants are very aggressive. They attack when the nest or foraging column is disturbed, and produce a strong, distinctive odor.

Identification
Shattuck (1992) - Worker: Polymorphic. majors with ocelli; anterolateral clypeal margin with the comers expanded slightly anterior ofthe mediolateral region; anteromedial clypeal margin with a broad. shallow concavity; mandible with about 7 to 9 teeth. an indistinct basal angle. and 3 to 5 denticles on the basal margin; metanotal groove reduced to a suture and with the mesonotum and propodeum forming a continuous. uninterrupted surface; petiolar scale vertical and not inclined anteriorly. Western North America from southern Canada south to central Mexico; Italy east to the Caspian Sea; eastern India east through southern China. Queen: Venter of the petiole with a well developed. angular lobe; 75 to 100 short. erect hairs on the mesoscutum; anteromedial clypeal margin with a broad. shallow concavity; basal angle of mandible indistinct. with a relatively uninterrupted curve between the masticatory and basal margins; petiolar scale vertical and not inclined anteriorly. Male: Basal margin of mandible denticulate distally. smooth proximally; episternal suture reduced or absent; fore wing with two closed cubital cells; paramere enlarged.

Workers can be recognized by the configuration of the anterior clypeal margin and the even arch of the dorsal mesosomal surface

Identification Keys

 * Key to US Liometopum species

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Species of this genus are found in the Holarctic Region as far south as southern México. This genus is very common in New Mexico; nests are usually located under stones or in living trunks or dead logs. Colonies are very large, probably numbering in the thousands or tens of thousands. The ants are very aggressive, and although they do not sting, they can be very unpleasant. (Mackay and Mackay 2002)

Efforts to locate colonies may be very exasperating: "While collecting in Colorado during the summer of 1903, I made repeated attempts to get at the nest of Liometopum .... The files of ants were often seen disappearing under rocks, but when these were lifted in the hope of finding their nests, it was found that only a runway or perhaps a succursal nest had been uncovered. In vain rocks were removed over large surfaces, only to find the burrow at last disappearing into the ground under the roots of some great tree, immovable boulder or cliff. The fact that in these runways the ants often congregate in numbers ... is apt to lead the observer to believe that he has found the nest, but these cavities contain no larvae, males, or females, and careful inspection shows that they lead off into a continuation of the runway. The cavities are, in fact, mere temporary resting places for the out- and home-bound companies of workers" (W.M. Wheeler, 1905:330).

Nomenclature

 *  LIOMETOPUM [Dolichoderinae: Tapinomini]
 * Liometopum Mayr, 1861: 38. Type-species: Formica microcephala, by monotypy.

Description
Shattuck (1992):

Worker
HEAD. Vertex concave. Compound eyes present. approximately round; relatively anterior on head. Ocelli present (in majors). Antennae 12 segmented. Scape short. at most surpassing the vertex by less than one-third its length. Anterolateral clypeal margin with the corners expanded slightly anterior of the mediolateral region. Anteromedial clypeal margin with a broad. shallow concavity. Anterior clypeal setae 6-12; short. less than twice the maximum scape diameter; straight. Posterior clypeal margin even with or posterior to the posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Frontal carina present. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUlHPARTS. Palp formula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp segment at the apical extreme of segment 4. Mandible with 7-9 teeth and no denticles. Apical tooth subequal in length to the subapical tooth. Basal angle indistinct, with a relatively uninterrupted curve between the two margins. Basal margin denticulate along entire surface. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Declivitous and dorsal faces of propodeum convex; dorsal face subequal in length to the declivitous face. Propodeal angle indistinct. Mesosomal spines and tooth absent. Erect pronotal hairs 16-45; elongate, much longer than the maximum scape width. Dorsal pro-mesonotal junction with the pronotum and mesonotum even. Metanotal groove reduced to a suture and with the mesonotum and propodeum forming a continuous, uninterrupted surface. Metanotal spiracle lateral and ventral of the dorsal surface when viewed in lateral profile. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). PETIOLE. Scale present; ridged and with a distinct angle dorsally (tapering dorsally into a broad point); vertical and not inclined anteriorly. Venter with a slight or weakly developed lobe. GASTER. First tergite vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the basal portion of the petiole. Anterior tergosternal suture of the first segment extending laterally from the helcium in a distinct arch which extends dorsal of the dorsal helcial surface. Fifth tergite ventral, gaster with 4 apparent tergites. Gastral compression absent (gaster circular in cross section). Fourth sternite keel-shaped posteriorly. GENERAL CHARACTERS. Worker caste polymorphic. Chromosome number unknown. Integument thin and flexible, weakly sculptured. PROVENTRICULUS. Cupola much broader than bulb; round; with long pile; smooth, without sculpture; and without phragma. Bulb exposed in lateral view. Longitudinal muscle No.1 present. Occlusory tract present.

Queen
HEAD. Vertex weakly concave. Compound eyes relatively anterior on head. Antennae 12 segmented. Scape short, surpassing the vertex by less than one- half scape length. Anterolateral clypeal margin even with the mediolateral region. Anteromedial clypeal margin with a broad, shallow concavity. Anterior clypeal setae about 1 0; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp segment at the apical extreme of segment 4. Mandible with 7-9 teeth and no denticles. Apical tooth slightly longer than the subapical tooth. Basal angle indistinct, with a relatively uninterrupted curve between the two margins and without a distinct tooth or angle. Basal margin denticulate distally, smooth proximally. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture com124 plete. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Axilla parallel and entire. Anterior axillar suture straight. Declivitous and dorsal faces of propodeum convex; dorsal face subequal in length to the declivitous face. Propodeal angle distinct. Propodeal suture absent. Mesosomal spines and tooth absent. Erect mesoscutal hairs about 75- 100; short, less than twice the maximum scape diameter. Propodeal spiracle lateral and ventral of the propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). WI NGS. Radial cell closed. Fore wing with 2 cubital and 1-2 discoidal cells. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally (narrowed dorsolaterally); vertical and not inclined anteriorly. Venter with a well developed, angular lobe. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the basal portion of the petiole. Fifth tergite vertical and with the distal terminus of the gaster not well defined. Gastral compression absent (gaster circular in cross section). Fourth stemite flat across entire posterior border.

Male
HEAD. Inner margin of eye entire, flat. Scape length at most only slightly longer than the length of funicular segments 1 +2+3. First funicular segment cylindrical or cone-shaped. Second funicular segment cylindrical, straight. Funicular segments 2 and 3 at most twice as long as broad. Third and fourth funicular segments straight. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 1 0-20; short, about twice antennal diameter; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. MOUTHPARTS. Palpformula 6:4. Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp at the apical extreme of segment 4. Mandible with 7-1 0 teeth and 0-1 denticles. Apical tooth slightly longer than the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin denticulate distally, smooth proximally. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture reduced and incomplete (always weakly developed posteriorly), or absent. Anteromedial mesosternum even with the lateral regions. Axilla constricted medially and entire. Anterior axillar suture straight. Declivitous and dorsal faces of propodeum convex; dorsal face subequal in length to the declivitous face. Propodeal angle distinct. WINGS. Radial cell closed. Fore wing with 2 cubital and 1 discoidal cells. Pterostigmal appendage absent. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally, or spined and with a double tooth or projection dorsally; vertical and not inclined anteriorly. Venter with a well developed lobe. Attachment to gaster narrow. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the entire height of the petiole. GENITALIA. Pygostyles present. Posterior margin of sub genital plate concave or with a 'V"shaped notch. Paramere entire (but with a very weak suture). Digitus with a down-turned tip. Cuspis slightly ventral of digitus. Ventral lobe of volsella present as concave lobe. Aedeagus with ventral teeth.

Larva
Body hairs sparse; simple; short. 10 spiracular pairs. Antennae large.