Crematogaster is an ecologically diverse genus of ants found worldwide, which are characterised by a distinctive heart-shaped gaster (abdomen), which gives them one of their common names, the Saint Valentine ant.[2] Members of this genus are also known as cocktail ants because of their habit of raising their abdomens when alarmed.[3] Most species are arboreal (tree-dwelling). These ants are sometimes known as acrobat ants.[4]
Cocktail ants acquire food largely through predation on other insects, such as wasps.[5] They use venom to stun their prey and a complex trail-laying process to lead comrades to food sources. Like most ants, Crematogaster species reproduce by partaking in nuptial flights, where the queen acquires the sperm used to fertilize every egg throughout her life.[citation needed]
Predatory behavior
Cocktail ants hunt both large and small prey. When time to hunt, foragers typically recruit nearby ants to assist them. The ants can mark and detect their prey by specific contact. When they make contact, they attack, sometimes releasing a small amount of venom with a sting. They also release an alarm pheromone to alert still more workers that prey has been seized. If other workers are present, the ants "spread-eagle" the prey. When the prey is spread-eagled, all limbs are outstretched and it is carried along the backsides of the ants. The ants carry arolia, pad-like projections that are used to carry the prey back to the nest. These arolia are critical because cocktail ants are arboreal and often need to travel up trees to return to their nesting location. If the prey is small and only one ant is present, it can carry the prey individually. If other workers are present, the ant recruits carrying assistance, even if the prey is small. Cocktail ants typically eat grasshoppers, termites, wasps, and other small insects.[6] South American Crematogaster ants are also known to feed on egg sacs and spiderlings from the colonies of the social spider Anelosimus eximius.[7]
Predation of wasps
Cocktail ants are known to eat different types of wasps. Many of these wasps have mutualistic relationships with trees involving pollination.[8] Additionally, the wasps typically have cycles that they follow, which can make locating and capturing them by the ants more difficult. As a result, cocktail ants have evolved unique characteristics to detect the presence of prey. They have become sensitive to chemical signals released by wasps, and use these signals as cues in locating their prey.[5]
Cocktail ants can be found either outdoors or indoors with great frequency in each case. Outdoors, they are usually arboreal, but they often live in many common areas in the wild. These areas are typically moist and are often dark. They can often be found in trees, collections of wood (like firewood), and under rocks. Indoors, nests have been found inside homes around electrical wires.[9] These locations are often very near large food supplies and may be around other ant nests.[citation needed]
Reproduction
As with many social ant species, in cocktail ants, a queen mates with a single male during a nuptial flight. During this flight, the winged queen and winged male mate, and the male dies shortly afterwards. The female eventually lands and removes her own wings, which she no longer needs.[citation needed]
In these ant species, a variation also exists to this mating strategy. Large female workers exist that are smaller than winged queens, yet larger than small workers. They also have many anatomical features that are intermediate to small workers and the queen, including ovary size and composition, and patches. These females can produce unfertilized eggs that can eventually develop into males in colonies that do not have a queen. If these eggs are produced in a colony with a queen, the queen can devour them. Larvae can also devour the eggs. Large workers normally produce more eggs in ant colonies that are queenless. Large workers can be tended to by small workers in a similar manner to ant queens.[10]
Defensive behavior
Crematogaster ants "are able to raise their abdomens forward and over their thoraces and heads, which allow them to point their abdominal tips in nearly all directions",[11] "as if they were performing a balancing act",[12] thus they are colloquially known as cocktail ants or acrobat ants.
When in conflict, cocktail ants can release a venom by flexing their abdominal regions. The effectiveness of the venom varies greatly with the opposer to the ant. For example, some other ant species are not very resistant and can be killed with only a few drops, while other ant species and insects have a high degree of resistance to even large amounts of venom. However, the venom can often repel offending ants if it comes into contact with their antennae. Cocktail ants are typically not repelled by venom from other cocktail ants. The venom is created in a metapleural gland and usually consists of complex and simple phenols and carboxylic acids, some of which have known antibiotic properties.[13] The ants apply froths to conflicting organisms. The froths are applied in a "paintbrush" style manner to surround the offender. "Frothing" has evolved independently in ants and grasshoppers.[14]
Division of labor
As with most eusocial insects, cocktail ants tend to form castes based on labor duties. This division is normally behavioral, but also has a physical basis, including size or age.[15] Soldiers are typically larger with a more developed metapleural gland specialized for colony defence or food acquisition. A worker ant is generally smaller than soldiers and queens, and its main task is to assist the queen in rearing the young. Workers vary in size more than soldiers. This considerable variation in size may have played a considerable role in the evolution of "large workers" in this genus.[16]
Mutualism
Cocktail ants participate in a form of mutualism called myrmecophytism, in which plants provide shelter and secreted food, while the ants provide the plants with protection from predators. Many cocktail ants use plants such as Macaranga as their main source of food.
The ants become alarmed when the plant is disturbed. They quickly emerge from their plant shelter and become aggressive. This can be the case even when neighboring plants are under attack. They can also recruit other ants to help in their defense.[17] 3-Octanone and 3-Octanol have been identified as the alarm pheromones of East African Crematogaster negriceps and Crematogaster mimosa.[18] The major components of the mandibular secretion of the Costa Rican Crematogaster rochai are also 3-octanone and 3-octanol.[19]
Trail-laying
Cocktail ants lay scent trails for many different reasons - communication, recruitment of workers, etc. The scents originate in the tibial gland and are secreted from the gaster of the ants. The gaster never actually touches the surface of what the ant is leaving the scent on. When laying a scent trail, the ants will typically lift their abdomen sharply upward then bend it forward.[20]
One practical use for trail laying is to mark the path toward food. The ants often find a food source requiring them to make multiple trips to the nest or shelter. To keep track of space, a scent is useful. Another significant use of a scent is to recruit other workers. This is actually helpful in a number of scenarios. It can increase efficiency when a food source is located and needs to be brought back to the nest. It can also be helpful in recruiting assistance during an attack on one of the cocktail ants' plant shelters.[citation needed]
Species
More than 430 species are recognised in the genus Crematogaster:[1]
Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and in soil, rotting wood, under stones, or in trees.
Pogonomyrmex is a genus of harvester ants, occurring primarily in the deserts of North, Central, and South America, with a single endemic species from Haiti.
Tapinoma is a genus of ants that belongs to the subfamily Dolichoderinae. The genus currently comprises 74 described species distributed worldwide in tropical and temperate regions. Members of are generalized foragers, nesting in a wide variety of habitats, ranging from grasslands, open fields, woodlands, to inside buildings. The majority of species nest in the ground under objects such as stones or tree logs, other species build nests under bark of logs and stumps, in plant cavities, insect galls or refuse piles.
Aphaenogaster is a genus of myrmicine ants. About 200 species have been described, including 18 fossil species. They occur worldwide except in South America south of Colombia, sub-Saharan Africa, and Antarctica.
Plagiolepis is an ant genus of the formic acid-producing subfamily Formicinae. The genus is found in tropical and temperate regions of the Old World.
Tetramorium is a genus of ants in the subfamily Myrmicinae that includes more than 520 species. These ants are also known as pavement ants.
Crematogastrini is a tribe of myrmicine ants with 64 genera and 8 fossil genera.
Aenictus is a large army ant genus distributed in the Old World tropics and subtropics. It contains about 181 species, making it one of the larger ant genera of the world.
Anochetus is a genus of small, carnivorous ants found in the tropics and subtropics throughout the world.
Hypoponera is a genus of ants in the subfamily Ponerinae. The genus has a worldwide distribution and is found in all continents except Antarctica.
Dolichoderus is a genus of ants found worldwide.
Vollenhovia is a genus of ants in the subfamily Myrmicinae.
Carebara is a genus of ants in the subfamily Myrmicinae. It is one of the largest myrmicine genera with more than 200 species distributed worldwide in the tropics and the Afrotropical region. Many of them are very tiny cryptic soil and leaf-litter inhabitants. They nest in rotten wood to which the bark is still adherent in the Afrotropical region, or may be lestobiotic nesting near other ant species. Some species are known to exist parasitically within termite nests. Little is known about the biology of the genus, but they are notable for the vast difference in size between queens and workers.
↑ African Insect Life - S. H. Skaife (Longmans, Green— Cape Town)
↑ Acrobat Ant, Iowa State Univ., Dept. of Entomology
1 2 Schatz, Bertrand, and Martine Hossaert-Mckey. "Interactions of the Ant Crematogaster Scutellaris with the Fig/fig Wasp Mutualism." Ecological Entomology 28.3 (2003): 359-68. Print.
↑ Richard, Freddie. "Predatory Behavior in Dominant Arboreal Ant Species: The Case of Crematogaster Sp. (Hymenoptera: Formicidae) - Springer." Predatory Behavior in Dominant Arboreal Ant Species: The Case of Crematogaster Sp. (Hymenoptera: Formicidae) - Springer. N.p., 01 Mar. 2001. Web. 24 Oct. 2013.
↑ Schatz, Bertrand, Marie-Charlotte Anstett, Welmoed Out, and Martine Hossaert-McKey. "Olfactive Detection of Fig Wasps as Prey by the Ant Crematogaster Scutellaris (Formicidae; Myrmicinae)." Naturwissenschaften 90.10 (2003): 456-59. Print.
↑ Nauman, Jennifer S. "Acrobat Ants.": College of Agriculture, Forestry and Life Sciences: Clemson University: South Carolina. N.p., n.d. Web. 22 Nov. 2013.
↑ Heinze, J., S. Foitzik, B. Oberstadt, O. Rüppell, and B. Hölldobler. "A Female Caste Specialized for the Production of Unfertilized Eggs in the Ant Crematogaster Smithi."Naturwissenschaften 86.2 (1999): 93-95. Print.
↑ Schulz, Stefan (7 January 2005). The Chemistry of Pheromones and Other Semiochemicals II. Springer Science & Business Media. p.193. ISBN9783540213086.
↑ Marlier, J., Y. Quinet, and J. Debiseau. "Defensive Behaviour and Biological Activities of the Abdominal Secretion in the Ant Crematogaster Scutellaris (Hymenoptera: Myrmicinae)." Behavioural Processes 67.3 (2004): 427-40. Print.
↑ Stapley, L. "Physical Worker Castes in Colonies of an Acacia-ant (Crematogaster Nigriceps) Correlated with an Intra-colonial Division of Defensive Behaviour." Insectes Sociaux 46 (1999): 146-49.
↑ Peeters, Christian, Chung-Chee Lin, and Yves Quinet. "Evolution of a Soldier Caste Specialized to Lay Unfertilized Eggs in the Ant Genus Crematogaster (subgenus Orthocrema)." Elsevier 42 (201 a3): 257-64. Web. 10 Nov. 2013.
↑ Inui, Yoko, and Takao Itioka. "Species-specific Leaf Volatile Compounds of Obligate Macaranga Myrmecophytes and Host-specific Aggressiveness of Symbiotic Crematogaster Ants." Journal of Chemical Ecology 33.11 (2007): 2054-063. Print.
↑ Wood, William F.; Chong, Berni (1975). "3-Octanone and 3-Octanol; Alarm Pheromones from East African Acacia Ants". Journal of the Georgia Entomological Society. 10: 332–334.
↑ Wood, William F. (2005). "Comparison of mandibular gland volatiles from ants of the bull horn acacia, Acacia collinsii". Biochemical Systematics and Ecology. 33 (7): 651–658. Bibcode:2005BioSE..33..651W. doi:10.1016/j.bse.2004.12.009.
1 2 Hosoishi, S. & Ogata, K., 2009, A taxonomic revision of the Asian endemic subgenus Physocrema of the genus Crematogaster (Hymenoptera: Formicidae)., Zootaxa (2062), pp. 15-36: 29-30
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