Liometopum apiculatum

Liometopum apiculatum is a species of ant in the subfamily Dolichoderinae. Liometopum apiculatum ants are found in arid and semi-arid regions of southwestern United States and Mexico to Quintana Roo. Liometopum apiculatum was first described by Mayr (1870), who described the workers of this species. Emery (1895) later described the queens of this species; Wheeler (1905) described the males and Wheeler & Wheeler (1951) described the larvae. Shattuck (1994) considered L. apiculatum a senior synonym of Liometopum masonium. This species was also confirmed by Del Toro et al. (2009). Liometopum apiculatum ants are found in arid and semi-arid regions of southwestern United States and Mexico to Quintana Roo. They extend from Colorado through Texas, New Mexico, southeastern Arizona, and south into Mexico. They are usually found at elevations of 1,000–2,500 metres (3,300–8,200 ft), but their prime habitat is oak forests found around 2,000 m (6,600 ft). At higher elevations they are found in pinyon pine zones, up to the ponderosa pine and riparian zones; at lower elevations they inhabit creosote bush scrub and grasslands in microhabitats of clay, under rocks, boulders, and decaying logs. They have also been found in foothill meadows, deciduous canyon forests, pinyon-cedar woodlands, ponderosa pine-cedar-oak woodlands, and cottonwood–willow forests. At high elevations, their abundance decreases and they are replaced by L. luctuosum. Altitude may play an important role in the distribution of Liometopum. In regions of Mexico explored by Conconi et al. (1983b), L. luctuosum and L. apiculatum are only found between 2,000 and 3,000 m (6,600 and 9,800 ft). Although conditions below 1,800 m (5,900 ft) looked favorable, they are absent. In the U.S., L. apiculatum is found from 1,316 to 2,438 m (4,318 to 7,999 ft). Nests of L. apiculatum are typically located underground and have a very distinctive structure. They fill hollowed-out chambers with a branched network of carton-like material made out of agglomerated soil and oral secretions until the entire nest resembles Swiss cheese. Within the nest as many as three or four large chambers containing this honeycombed carton-like material can be found. The carton-like material of this species is much finer than that of L. uctuosum. L. apiculatum tend to nest at higher densities than do L. luctuosum. These ants are usually found nesting in dead logs, under stones, or in decaying stalks of Yucca spp. They have also been collected in glass containers and rubber tires and among the roots of various perennial xerophytes such as Agave spp., Opuntia spp., Myrtillocactus geometrizans, Yucca filifera, Senecio praecox, Schinus molle or Prosopis juliflora. In some habitats, the nests are deep under heavy boulders or large trees. The queen is always well protected and is usually in a remote place about 6–8 m (20–26 ft) from the largest chamber where the brood is stored. The chambers are connected by various galleries. Colonies of L. apiculatum are polydomous with segments of nests (or satellite colonies) scattered over the land scape. Colonies are variable in size, ranging from a few hundred to hundreds of thousands of workers. Colonies exploited for their brood by humans contain between 65,000 and 85,000 individuals, while undisturbed colonies may contain as many as 250,000 individuals. Colonies remain useful for repeated brood collection by humans for 4 to 12 years. Colony foundation in L. apiculatum is by haplometrosis (non-cooperative), that is, a single fertile queen founds each colony. Colony foundation behavior is not uniform among founding queens. The time spent exploring, excavating, and removing excavated materials and waste are usually higher throughout the day, while oviposition, brood care, and inactivity increase at night. Founding queens prefer sites close to bodies of water; however, sites slightly further from water are more conducive to the establishment of a successful colony as persistently high humidity will result in the early death of a colony due to fungal invasion. Liometopum apiculatum are opportunistic carnivores and granivores, and have also been observed foraging on dead insects, larger colonies being more predaceous. L. apiculatum also feeds on crustaceans, annelids, mollusks, dead vertebrates, animal droppings, and extrafloral nectar. These ants also obtain nectar or pollen from bear grass and substances from the outside of the ovaries of the flowers of century plants (Agave scabra and Agave chisosensis) and Spanish dagger (Yucca spp.). Workers have been attracted to various foods used as baits including apple sauce, sausage, vegetable soup, sugar water, and cookies. L. apiculatum have also been observed soliciting honeydew from insects including membracids (Vanduzea segmentata), aphids, and other ants (Pogonomyrmex barbatus, Camponotus sayi and Solenopsis xyloni). In some habitats the honeydew produced by hemipterans, Cinara spp., Dysmicoccus brevipes and Saissetia oleae, are the main energy sources. In other words, hemipteran exudates make up the bulk of the diet of L. apiculatum. Their role in disrupting biological control has not been determined. Liometopum apiculatum forage from March to September. Workers forage almost exclusively on trails as wide as 2–3 cm (0.8–1.2 in) on the soil surface, and when the temperature rises sharply at midday, they cease foraging and seek shelter under stones. The movement of this species is less erratic than L. occidentale at higher temperatures. An increase in temperature by 30 °C (54 °F) changes the speed 15-fold, increasing exponentially from 0.44 to 6.60 cm (0.17 to 2.60 in) per second. There also appears to be little difference in the speed whether ants are moving towards or away from the nest, or between large and small workers during the summer months. However, after prolonged periods (two months or more) of low temperatures, the larger workers are faster than the small workers. Also within a range of 14–38 °C (57–100 °F), there appears to be little effect of temperature on the number of ants on trails. Maximal activity occurs between 12 p.m. and 12 a.m during the summer months in southern alpine habitats such as Mount Wilson, California. In natural environments, ants of this species forage in areas of 468–708 m2 (5,040–7,620 sq ft), with an average of 612 m2 (6,590 sq ft); however, they only use between 16% and 30% of this area at any given time. The spatial distribution of the foraging areas for these species seems to be strongly correlated with the location of shrubs and trees infested by hemipterans.