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''Acromyrmex'' is a genus of New World ants of the subfamily Myrmicinae. This genus is found in South America and parts of Central America and the Caribbean Islands, and contains 31 known species. Commonly known as "leafcutter ants" they comprise one of the two genera of advanced attines within the tribe Attini, along with ''Atta''. ==Anatomy== ''Acromyrmex'' species' hard outer covering, the exoskeleton or cuticle, functions as armour, protection against dangerous solar waves, an attachment base for internal muscles, and to prevent water loss. It is divided into three main parts; the head, thorax, and abdomen. A small segment between the thorax and abdomen, the petiole, is split into two nodes in ''Acromyrmex'' species. The antennae are the most important sense organs ''Acromyrmex'' species possess, and are jointed so the ant can extend them forward to investigate an object. It can retract them back over its head when in a dangerous situation, for example, a fight. ''Acromyrmex'' species have eyes, but their eyesight is very poor. Like all insects, the eye is compound, meaning it is made up of many eyelets called ommatidia, with the number of these eyelets varies according to species. Male ants tend to have more ommatadia than other castes. The ocelli, which are generally found on top of the heads of queens, are thought to aid aerial navigation by sunlight. ''Acromyrmex'' is dark red in color. In addition to the standard ant anatomy, the back of the thorax has a series of spines which help it maneuver material such as leaf fragments on its back. ''Acromyrmex'' can be identified from the closely related ''Atta'' genus of leafcutter ants by their having four pairs of spines and a rough exoskeleton on the upper surface of the thorax compared to three pairs of spines and a smooth exoskeleton in ''Atta''. Much of the inside of the ''Acromyrmex'' head is occupied by the muscles that close the jaws; the muscles that open the jaws are much smaller. The brain, though tiny, is a very complex organ, and allows ''Acromyrmex'' to learn and react to its surroundings. It can remember colony odour, navigation, and where it has placed a certain object. The heart is a long, tubular organ running the entire length of the body, from the brain to the tip of the abdomen. It has valves within it that prevent blood from flowing the wrong way. The fluids bathing the internal organs is circulated by the heart; these fluids then filter through the organs and tissues. The pharynx, which is part of the gut, controlled by six muscles, pumps food into the oesophagus. Debris in the food, such as soil, is filtered before it enters the oesophagus and is collected in a tiny trap, the infrabuccal pocket. When this pocket becomes full, the ''Acromyrmex'' ant empties it into an area within or outside the nest designated as a waste-products area. Several glands in the head secrete various substances, such as those responsible for the digestion of food. Another gland within the head produces digestive and, in some species, alarm chemicals; these chemicals are used to alert nearby ants of impending danger, and any ant that detects this alarm will automatically go into "battle mode". If an ant is crushed, a huge blast of this chemical is released, causing the entire colony to go into "battle mode". The thorax contains muscles to operate the legs and wings and the nerve cells to co-ordinate their movements; also contained in this part of the body is the heart and oesophagus. The abdomen contains the stomachs, poison glands, ovaries in the queen, and the Dufour's gland, among other things. ''Acromyrmex'' ants have two "stomachs", including a dry, social stomach in which they can store food and later regurgitate to larvae, the queen and other ants. This is separated from the stomach proper by a small valve; once food enters the second stomach, it becomes contaminated with gastric juices and cannot be regurgitated. The exact function of the Dufour's gland is unknown, but is thought to be involved in the release of the chemicals used in the production of odour trails, which the ants use to recruit nest mates to a food source. It may also produce sex-attractant chemicals. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Acromyrmex」の詳細全文を読む スポンサード リンク
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