Acidopore. A small hole at the tip of the gaster through which formic acid and pheromones are released. The hole is surrounded by a characteristic fringe of hairs. The structure is present in, and only in, ants of the subfamily Formicinae. (top of page)
Antennal club. The terminal segments of the funiculus that appear enlarged relative to the other segments. The antennal clubs referred to in PIAkey are restricted to the Myrmicinae, and are composed of either two or three segments. (top of page)
Antennal club, three-segmented. The three terminal segments of the funiculus are enlarged relative to the other segments. (top of page)
Antennal club, two-segmented. The two terminal segments of the funiculus that are enlarged relative to the other segments. (top of page)
Antennal scape. The first, elongated segment of the antennae that attaches to the head. (top of page)
Antennal scrobe. A groove recessed in the head to receive all or a portion of the antennal scape. Often margined by the frontal carinae. (top of page)
Anterior. Towards the front (i.e. head or mandibles) of the specimen. Opposite of posterior. (top of page)
Apical. Towards the tip and away from the body or head. (top of page)
Bimorphic. Refers to species in which the workers are differentiated into subcastes of different sizes. In bimorphic castes (such as many Pheidole species) the workers develop into one of two discrete sizes (large or small). See also polymorphic and monomorphic. (top of page)
Clypeus, middle tooth present. The character state observed in Solenopsis invicta where the anterior margin of the clypeus is armed with one tooth in the middle (median) and one pair of side (lateral) teeth. The middle tooth is usually smaller than the side teeth, and the proper viewing angle is required for acurate assessment. The middle tooth tends to be more easily observed in smaller workers than in larger workers. (top of page)
Clypeus, middle tooth absent. The character state observed in Solenopsis geminata where the anterior margin of the clypeus lacks a middle (median) tooth, but possesses one pair of teeth that stradles the median. (top of page)
Clypeus. The most anterior section of the head adjacent to the mandibles. The anterior margin of the clypeus can be informative for species diagnosis. In particular, look for whether the anterior margin is indented, flat, convex or some specialized arrangement. (top of page)
Dolichoderinae. A subfamily of ants with one waist segment (petiole), and with the gaster armed only with a ventral slit. Some of the more notorious invasive ants in this subfamily include Linepithema humile, Tapinoma melanocephalum, and several species related to Technomyrmex albipes. (top of page)
Dorsal view. The view of a specimen achieved by looking directly at its dorsal surface. (top of page)
Dorsal. Pertaining to the dorsum, or upper surface. (top of page)
Eyes break outline of head. When examining the specimen in full face view, the eyes interrupt the the continuous curve of the head's margin. (top of page)
Eyes within outline of head. When examining the specimen in full face view, the eyes do not interrupt the continuous curve of the head's margin. All the PIAkey Dolichoderinae, in addition to several Formicinae, exhibit this character. (top of page)
Flagellate. See flagellate pilosity. (top of page)
Formicinae. A subfamily of ants characterized by a single waist segment (petiole) and with the gaster armed with an acidopore. Some of the more notorious invasive ants in this subfamily include Anoplolepis gracilipes, Paratrechina longicornis, and Paratrechina vaga. (top of page)
Frontal carinae. Elevated ridges that originate from the clypeus and extend posteriorly. In some ants, they form a margin of the antennal scrobes. (top of page)
Frontal lobes. Enlarged, lobe-like extensions of the frontal carinae that entirely or partially conceal the antennal sockets. Of the species included in PIAkey, they are most pronounced in the Ponerinae. (top of page)
Funiculus. All of the antenna excluding the scape. (top of page)
Gaster. The most posterior portion of the ant's body. Although this portion is sometimes referred to as the abdomen, it is only composed of the terminal 4 or 5 abdomenal segments. (top of page)
Head length. The distance from the posterior margin to the anterior margin of the head, as measured along the middle of the face. If either margin is indented, it is treated as if it was flat. (top of page)
Head shape, triangular. In full face view, the posterior margin of the head is significantly wider than the anterior margin. (top of page)
Head width. The maximum width of the head that can be measured in full face view. (top of page)
Head, posterior margin. The margin of the head that is farthest away from the mandibles. (top of page)
Mandibles, linear. Mandibles that are modified into long thin blades for specialized hunting, often with a fork of teeth at the end. Ants bearing linear mandibles are sometimes referred to as "trap-jaw" ants because suitable prey will trigger the mandibles to snap closed with incredible force. The two genera of trap-jaw ants included in PIAkey are the large, black Odontomachus, and the the minute Strumigenys. (top of page)
Mandibles, triangular. Mandibles that are approximately triangular in shape. This is the most common shape of most ant mandibles, and nearly all those included in PIAkey. (top of page)
Mandibles. The appendages of the head that ants use to bite, chew and hold objects. Mandibles come in a variety of shapes and sizes. Of the ants included in PIAkey, nearly all have triangular mandibles. The serations on the margins of the mandibles are referred to here as mandibular teeth. (top of page)
Mesonotum. The tergite of the mesosoma posterior to the pronotum. If the two are fused, they are together referred to as the promesonotum. (top of page)
Mesopleuron. The pleuron (lateral sclerite) of the mesothorax. It may be a single sclerite or divided into an upper anepisternum and lower katepisternum. (top of page)
Mesosoma, gradually sloped. A character state observed in myrmicine genera such as Cardiocondyla and Tetramorium in which the mesosoma is nearly flat and descends at a very gradual angle. (top of page)
Mesosoma, steeply sloped. A character state observed in the myrmicine genus such as Pheidole in which the mesosoma appears humped and descends at a sharp angle. (top of page)
Mesosoma. The middle of the three main body parts, to which the legs are attached. Also referred to as the alitrunk. Technically, it is not the thorax, because the first abdominal segment (the propodeum) is fused to it. (top of page)
Metanotum, impressed. In profile and dorsal view, the region between the mesonotum and propodeum is indented. (top of page)
Metanotum, not impressed. In profile and dorsal view, the region between the mesonotum and propodeum is not indented, but forms a continuous and uninterupted curve. (top of page)
Monomorphic. Refers to species in which the workers are not differentiated into subcastes of different sizes. See also bimorphic and polymorphic. (top of page)
Myrmicinae. A subfamily of ants characterized by the presence of two waist segments (petiole, postpetiole) and with the gaster armed with a sting. Some of the more notorious invasive ants in this subfamily include Solenopsis invicta, Pheidole megacephala, and Wasmannia auropunctata. (top of page)
Petiolar node, rounded. The shape of petiolar nodes that are evenly rounded and without distinct anterior, posterior or dorsal faces. PIAkey species with rounded petiolar nodes include Tetramorium lanuginosum, T. tonganum. (top of page)
Petiolar node, square-shaped. The shape of petiolar nodes with distinct anterior, posterior and dorsal faces. PIAkey species with square-shaped petiolar nodes include Tetramorium biacrinatum, T. simillimum and Wasmannia auropunctata. (top of page)
Petiolar node, wave-shaped. The shape of petiolar nodes with the anterior and dorsal faces rounded together and a distinct posterior face. PIAkey species with wave-shaped petiolar nodes include Tetramorium insolens and T. pacificum. (top of page)
Petiolar node. The raised portion of the petiole between the petiolar peduncle and the gaster. Reference in PIAkey is made to the petiolar nodes and peduncles of several Monomorium and Tetramorium species. (top of page)
Petiolar peduncle. The stem connecting the petiolar node to the propodeum. Reference is PIAkey is made to the petiolar nodes and peduncles of several Monomorium and Tetramorium species. (top of page)
Petiole. The first (most anterior) waist segment. The shape of the petiole is often an important character for taxonomic identification. In most genera it is raised, but in some, such as Tapinoma and Technomyrmex, it is flat. (top of page)
Pilosity, flagellate. Hairs that are long, thin and whip-like. In PIAkey, the only species with flagellate hairs is Strumigenys godeffroyi. (top of page)
Pilosity, spatulate. Hairs that are flat and become wider towards the end like a spatula. In PIAkey, the only genera with spatulate hairs are Pyramica and Strumigenys. (top of page)
Pilosity. A general term for hairs. Pilosity can be erect or appressed (close against the surface), long or short, thick or thin, light or dark. Paratrechina is often identified by characteristic pairs of long thick hairs arranged in rows. Strumigenys is known for highly modified flagellate and spatulate pilosity. (top of page)
Polymorphic. Refers to species in which the workers are differentiated into subcastes of different sizes. In bimorphic castes (such as many Pheidole species) the workers develop into one of two discrete sizes (large or small). In polymorphic castes (such as some Solenopsis, Monomorium and Camponotus species) the workers develop into a range of different sizes. (top of page)
Ponerinae. A subfamily of ants characterized by the presence of one waist segments (petiole) and with the gaster armed with a sting. Although few Ponerines are considered to be high-threat invasive species, species such as Odontomachus simillimus, Hypoponera opaciceps, and Pachycondyla stigma have spread throughout the Pacific Island area and beyond. (top of page)
Posterior. Towards the back, or gaster tip, of the specimen. (top of page)
Posterolateral lobes. Refers to the posterior sides of the head that are strongly developed in the major workers of Pheidole. Although this region has been referred to as the occipital lobes in previous literature, the term is not as morphologically accurate. (top of page)
Postpetiole. The second (most posterior) waist segment. Present in the Myrmicinae, but absent in the Dolichoderinae, Formicinae and Ponerinae. PIAkey makes particular use of the swollen postpetiole of Cardiocondyla species and Pheidole species. (top of page)
Preapical teeth. Teeth that precede the apical teeth (those occurring at the tip) of the mandibles. In PIAkey, reference is made to the preapical teeth of Strumigenys species. (top of page)
Profile. A view of the specimen achieved by looking directly at one side of the specimen. (top of page)
Pronotum. The most anterior tergite of the mesosoma. (top of page)
Propodeal declivity. The posterior face of the propodeum. Viewed in profile, it can be convex, flat or concave. (top of page)
Propodeal spines. A pair of spines projecting from the dorsal surface of the propodeum. The length of the spines can vary from long, (i.e. Wasmannia auropunctata) to short (i.e. Tetramorium simillimum), and can also vary within a species. The only subfamily in PIAkey with propodeal spines is Myrmicinae. (top of page)
Propodeal spiracle. An orifice (opening) located on the propodeum that is used for exchanging gases between the body of the ant and the atmosphere. The position, size and shape of the propodeal spiracle can be a good identification character. In PIAkey the only reference to the propodeal spiracle is made for distinguishing Pheidole fervens from P. oceanica. (top of page)
Propodeum. The posterior-most portion of the mesosoma. Sometimes referred to as the epinotum, it is in fact the first abdomenal segment that is fused to the thorax. (top of page)
Punctate sculpture. A rough surface created on the specimen resembling a multitude of pin pricks. In the field, a punctate sculpture can be identified by the dull, unreflecting appearance. Species of Monomorium, Cardiocondyla and Hypoponera afford good examples. (top of page)
Scape. See antennal scape. (top of page)
Scrobe. See antennal scrobe. (top of page)
Spatulate. See spatulate hairs. (top of page)
Spongiform appendages. Sponge-like structures that occur on the body parts (particularly the propodeum and waist) of some ant species. Spongiform appendages are prevelant among ants in the tribe Dacetini, including the genera Pyramica and Strumigenys. (top of page)
Sting. The sting is located at the tip of the gaster and can be used both as a defense against predators and as a weapon against prey. It is often connected to an internal venom sac. The only species included in PIAkey that have stings belong to the Myrmicinae and Ponerinae. However, some species can retract their stings, making them appear absent. (top of page)
Threat Level: High. Species considered by PIAkey to be of high threat level are documented as causing signficant harm to the environment, agriculture, human health, and/or quality of life. This designation is reserved for the two ant species (Solenopsis invicta and Wasmannia auropunctata) that pose the greatest threats to the people, ecosystems and food security of the Pacific Island region. Although it is recommended that all invasive ants be discouraged from establishing new populations and spreading into new localities, it is recommended that immediate action be taken if a new record of a high threat level species is discovered. (top of page)
Threat Level: Low. Species considered by PIAkey to be of low threat level have are not documented as causing signficant harm to the environment, agriculture, human health, and/or quality of life. Although many of these species can cause damage to one or more of the aforementioned categories, a discovery of a new invasion does not necessarily warrant the initiation of an emergency management plan. (top of page)
Threat Level: Medium. Species considered by PIAkey to be of medium threat level are documented as causing harm to the environment, agriculture, human health, and/or quality of life. Although these species are considered dangerous, they are either already widespread across the Pacific or are not believed to be harmful enough to warrant the initiation of an emergency management plan if discovered. (top of page)
Tibial spine, pectinate. A spine at the end of the hind tibia that is modified into a comb structure. In PIAkey, both Hypoponera and Pachycondyla have a pectinate hind tibial spur, but only Pachycondyla has a simple hind tibial spur. (top of page)
Tibial spine, simple. A spine at the end of the hind tibia that is unmodified, and does not appear similar to a comb. In PIAkey, this character is used to separate Hypoponera (absent) from Pachycondyla (present). In order to obtain a view of the structure, it may be necessary to manipulate the specimen until a favorable perspective is achieved. (top of page)
Waist. The portion of the body that connects the mesosoma to the gaster. Some ants, such as the Myrmicinae, have two waist segments (the petiole and postpetiole). Other ants, such as the Dolichoderinae, Formicinae, and Ponerinae) have only one waist segment (the petiole). (top of page)
Worker, major. A worker subcaste that is characterized by a larger size than other workers of the same colony. Major workers, sometimes referred to as soldiers, often exhibit disproportionately larger heads due to allometric growth. Genera within PIAkey that include species with a polymorphic worker caste include Pheidole, Solenopsis, Monomorium and Camponotus. Also see minor worker. (top of page)
Worker, minor. A worker subcaste that is characterized by smaller size than other workers of the same colony. Minor workers, sometimes referred to simply as minors, are often proportionally similar to workers of monomorphic species. Genera within PIAkey that include species with a polymorphic worker caste include Pheidole, Solenopsis, Monomorium and Camponotus. Also see major worker. (top of page)