Formicidae

Ants are 1-20 mm long and the body color ranges from yellowish brown to black. They are characterized by a large head and elbowed antennae. The antennae of females and workers are 10-12-segmented, and 10-13-segmented in males. Abdominal segment 2, or segments 2 and 3, are separated as distinct nodes. Colonies are comprised of individuals in three castes: workers, which are apterous neuter females; queens, which are reproductive females thatmay be winged, dealate, or apterous; and males, which are usually winged. Ants are successful social insects that occur in all zoogeographic zones, and their predominance in some ecosystems is linked to their strongly developed social organization and complex behavior, and on their ability to exploit a wide range of food sources. Most species forage for small arthropods or other invertebrates, but they also feed on plant products by directly feeding at flowers, or indirectly by tending homopterans and ingesting the honeydew they produce.

All species form long-lasting colonies, which are constructed in soil, living or dead wood, or plant crevices. The nest contains one or more reproductive females and a large number of workers and immatures. Males and virgin females are produced at specific times during the year. New colonies are usually produced by means ofa mating flight, where recently produced males and females fly from the parent nest and mate in the air or on the ground. After mating, the males die and one or more fertilized females shed their wings and form a brood chamber. Egg-laying begins soon after the brood chamber is built. Females do not feed during the development of the first brood. They nourish themselves and the first brood on the degeneration products oftheir wing muscles, fat body, and other energy reserves. Workers of the first brood leave the nest, forage, and feed the queen; they rapidly expand the nest and care for the next brood. The founding queen continues to lay eggs and remains in the nest. When the colony reaches a certain size the queen lays fertilized (diploid) eggs, which receive a special diet and treatment, and will develop into reproductive females. The queen lays unfertilized (haploid) eggs, which develop into males. The cycle of colony expansion and the production of reproductives may be repeated for many years.

The pest status of ants is based on their nesting and foraging habits. The urban environment provides a variety of soil types and conditions, such as open sun or shaded sites, wooded, field, or turfgrass, and these will be suitable for a large number of ant species. Food resources are not limited, since ornamental trees and shrubs usually sustain populations of aphids and other homopterans. These insects provide honeydew, which is the basic food for most ants. Nesting along building foundations can result in damage to structural members of buildings, and to exterior faces. The proximity of nests to buildings usually results in ants entering the building and finding food, then recruiting nestmates to the site. The persistence of ants foraging inside or the establishment of primary or satellite nests indoors is the basis of the pest status for most synan-thropic species. Ant species that are associated with trees or other plants in natural areas often accompany them when they are planted as ornamentals in urban areas. Cercopia obtusifolia trees in urban areas of the subtropics and neotropics may have associated with them colonies ofleaf-cutting ants, Acromyrmex octospinosus, Cercopia, and Azteca spp. In the USA, the rover ant Brachymyrmex deflis swarms in the spring and fall. Large numbers of winged females may collect in outdoor swimming pools.

The habit of foraging ants to visit a variety of food sources increases their potential to acquire pathogenic and food decay organisms. A large number ofpathogenic organisms have been recorded from ant species, including bacteria:

S. marcescens Shewanella putrefaciens Sphingomonas paucimoblis Staphylococcus aureus

Stenotrophomonas maltophila Vibrio parahaemolyticus V. fluvalis

Acinetobacter baumannii Aeromonas hydrophila Agrobacterium radiobacter Alcaligenes faecalis Burkholderia cepacia B. mallei Chryseobacterium meningosepticum Citrobacter frundii Clostridium spp. Enterobacter aerogenes E. cloacae E. durans

Enterococcus casseliflavus Escherichia coli 02 Klebsiella pneumoniae Micrococcus pyogenes aureus M. albus

Morganella morganii Proteus vulgaris Pseudomonas aeruginosa P. putida P. stutzeri P. vesicularis Salmonella spp. Serratia liquefaciens

The fungi reported from ants include: Aspergillus jlavus, A.fumigatus, A. niger, Cladosporium wernickii, Fusarium oxysporum, Penicillium spp., Scopulariopsis spp., and Syncephalastrum spp. The yeast reported from ants includes Gerotrichum candidum and Trichosporon cutaneum.

Acanthomyops

The workers are 3-4.5 mm long and usually light brown to yellowish brown; the body is shiny, and with few setae. Antennae are 12-segmented and without a club; maxillary palps are three-or four-segmented; eyes are small. The epinotum is without spines and the pedicel is one-segmented. Workers are capable of emitting a pleasant odor similar to citronella when alarmed or crushed. Citronellal and citral are produced in the mandibular glands, and these chemicals probably function as an alarm pheromone. A formic acid odor may be detected when the gaster is crushed. They are nocturnal and nest below ground; they usually collect honeydew from aphids (Prociphilus, Anur-aphis) that suck sap from plant roots. During winter, entire colonies, including workers and winged forms, may move next to house or building foundations. Nests are established in cracks and crevices in the foundation, but they rarely forage indoors. When reproductives swarm in large numbers in basements and around the outside of buildings, they may be mistaken for termites. Workers of A. claviger have been used in anting by starlings (Sturnus vulgaris), and winged males and females have been used in anting by bluejays (Cyanocita cristata). Anting is the behavior of some birds which place live ants within their feathers; the ants may remove parasites from the bird's body and feathers.

Smaller yellow ant, Acanthomyops claviger (Fig. 9.2a) Workers are 3-4 mm long and the head and thorax are brown; the gaster is dark brown. The scape does not extend beyond the posterior margin of the head, and the apical segments of the antenna are distinctly clavate. The pedicle is narrow and sharp at its peak. Nests are in open woodlands, pastures, and grassy fields. In the urban environment, nests may be in soil surrounding buildings. Colonies are of moderate size and probably with a single queen. Natural food is primarily honeydew from subterranean aphids and other homopterans. Winged reproductives emergefromAugustto November. Large

Figure 9.2 Hymenoptera: Formicidae. (a) Acanthomyops clauiger; (b) A. latipes; (c) A. murphyi; (d) Aphaenogaster fulua; (e) A. lamellidens; (f) A. tennesseensis; (g) A. rudis; (h) Atta texana.

numbers of males and females may fly from the nest at one time, and several of these flights may occur and involve 40 00060 000 individuals. Winged forms may overwinter in nests and they are often released during warm periods in winter. This species is native to North America, and it occurs generally throughout the USA and southern Canada.

Larger yellow ant, Acanthomyops interjectus (Fig. 9.3a, b)

Workers are 4-4.5 mm long and yellowish brown to brown. The scape extends beyond the posterior margin of the head. The dorsum of the gaster has long setae, which are largely confined to the first gastric segment, and to the posterior border of the succeeding segments. Nests are usually in exposed soil or under the cover ofstones or logs. In open areas, the nests are in mounds. In the urban environment, nests may be around the perimeter and along the foundation ofbuildings, and under concrete slabs. Colony activity, such as nest construction and foraging, is primarily at night. Winged forms emerge from nests from March to July, and these individuals may have been produced in the colony the previous year. Indoors, swarming may occur from late fall to early spring. Natural food is honeydew produced by root-feeding homopterans and other subterranean insects. Indoors they forage for household foods. This species is native to North America, and it occurs generally throughout the USA and southern Canada.

Acanthomyops latipes (Fig. 9.2b) Workers are 3.5-3.7 mm long and brown to dark brown. The scape extends to or slightly beyond the posterior border of the head; antennal segments 6-11 are enlarged. The pedicel is thick and blunt at the apex.

Figure 9.3 Hymenoptera: Formicidae. (a) Acanthomyops interjectus, winged queen; (b) A. interjectus, worker; (c) Camponotus pennsyluanicus, winged queen; (d) C. pennsyluanicus, minorworker; (e) C. pennsyluanicus, majorworker; (f) C. pennsyluanicus, dealate queen.

Setae on the body are long, especially on the gaster; setae are present on the cheeks, gula, and the pedicel. Nests are in open woodlands, grassy fields, and meadows, and usually in dry soils. In the urban environment, nests are often around building foundations, but it is infrequently found indoors. In open areas, nests are in earthen mounds that are 30-45 cm diameter and 2-8 cm high. Mounds have vegetation growing from them and a large number of entry and exit holes. Natural food is honeydew of subterranean aphids and other homopter-ans that are feeding on the roots of wild and domesticated plants. Winged forms are produced in the colony in summer, and they emerge in August and September. Some of the males and winged females may remain in the nest over the winter and emerge the following spring. New colonies are often formed by a fertilized queen becoming a temporary parasite in the nests of another species of ant, and most likely one of the Lasius species. This species is native to North America, and it ranges from Alaska and Quebec, Canada, south to New Mexico and South Carolina.

Acanthomyops murphyi (Fig. 9.2c) Workers are 3-3.7 mm long and yellowish brown to brown. The eye has about eight ommatidia at its greatest diameter, which is about 0.10 mm. Fine setae are abundant on the epinotum and pedicel. The scape extends to the posterior margin of the head or slightly beyond. The apex of the petiole is blunt. Nests are in open woods and below stones and other objects on the ground. In urban areas, the nest may occur infrequently around the perimeter of buildings. Natural food is honeydew from subterranean aphids and mealybugs that are feeding on plant roots. Although this species may nest around buildings, there are no records of them foraging indoors. Winged forms emerge from the nest in June and July; these individuals may be produced in the colony the previous year and overwintered in the nest. A. murphyi is native to North America, and in the USA it ranges from Montana to Ontario, Canada, south to Colorado and Georgia. It is rare in all parts of its range.

Aphaenogaster

This large genus has several species that are common in urban habitats. Workers are 4-6.5 mm long and slender; it has long legs and 12-segmented antennae with an indistinct four-segmented club. The epinotum has prominent spines and the pedicel is two-segmented. These species usually have solitary foragers in leaf litter above ground and take a variety of foods. They nest in decayed wood, under stones, and in soil, where they often make an elevated area where they have deposited soil from the nest excavation. Nests have about 3500 workers and several queens.

Aphaenogaster fulva (Fig. 9.2d) Workers are 3.5-5.8 mm long and the body is pale brown to dark brown. The gaster and appendages are dark brown. The mesonotum has the anterior border strongly produced to form a transverse swelling, which may be depressed in the center. Epinotal spines are long and pointed upwards. Nests are in rotting wood, such as logs or stumps, and in the soil beneath stones and other objects. They may nest around the foundation of buildings and houses. Natural food is live and dead insects; they are notknown to eat honeydew. This species is distributed in eastern USA.

Aphaenogaster lamellidens (Fig. 9.2e) Workers are 4.1-6.5 mm long; the head, thorax, and petiole are reddish brown. The gaster is yellowish brown, and antennal segment 1, femora, and tibiae are dark brown to blackish brown. The outer face of the frontal lobe has a flange, which projects posteriorly in the form of a tooth. Colonies have 500-3000 workers and they are established in wood and in structural sites. Natural food includes live and dead insects; they are not known to eat honeydew. This species is native to North America and occurs from Illinois to New York and south to Louisiana and Florida.

Aphaenogaster tennesseenis (Fig. 9.2f) Workers are 4.1-5.3

mm long, and the head, thorax, and petiole are reddish brown. The gaster is yellowish brown, and the appendages are dark brown. The mesonotum is strongly pronounced anteriorly, and the thorax is strongly sculptured. Epinotal spines are long and pointed, and there are few erect setae on the dorsal surface of the body. The female body appears polished. Nest sites include decaying logs and stumps, or in decayed sites in living or dead trees. This species is found in wooded areas. Natural food includes live and dead insects, and honeydew. This species is native to North America, and it occurs from South Dakota and Ontario, Canada, south to Oklahoma and Georgia.

Aphaenogaster rudis (Fig. 9.2g) Workers are 4.5-5 mm long and the body color is pale brown to dark brown, while the antennae and legs are light brown. The body is covered with erect setae. Sculpturing on the head varies from longitudinal ridges to punctate, and the pronotum may be punctate or with ridges. Epinotal spines are short, and seldom as long as the base of the epinotum. Nests are in exposed soil, leaf litter, under stones, or in logs or decaying wood. Colonies have 500-3500 individuals. There is one functional queen, but there may be 2-15 other females present, perhaps the result of the fusion of several colonies. Immature stages of this species pass the winter as eggs and larvae. Natural food includes seeds, pollen of ground-nesting bees, and other insects, which are killed and eaten. This species is native to North America, and it occurs from Illinois to Massachusetts, south to Colorado and Florida.

Atta

These are leaf-cutting ants. The reddish-brown workers are 1.5-12 mm long; the legs are long. Their body is usually densely punctate, and covered with fine setae. The head has distinct spines, and the antennae are 11-segmented and without a distinct club. The thorax has three prominent spines, the anterior pair being the largest; the pedicel is two-segmented, and the gaster is rounded. Nests are below ground and usually in well-drained sandy or sandy-loam soils. The workers cut pieces of leaves and usually carry them above their head back to the nest in long columns. In the nest, the leaves are made into a substrate for growing fungi; these ants feed on fungi growing in the nest. A mature colony contains thousands of individuals, including a large-headed soldier caste.

Texas leaf-cutting ant, Attatexana (Fig.9.2h) Workers are4-14 mm long and they are extremely polymorphic, with some workers being very large. The body color is dull brown to reddish or orange brown, and the body is densely punctate. The head is strongly bilobed and the mandibles are large and flattened with numerous teeth. Each occipital lobe has two spines: a large one at the posterior corner of the head, and a small one anterior to it. The thorax has three pairs of prominent spines, with the anterior ones the largest. The legs are very long. Nests are in the ground and usually in well-drained sandy or loamy soils. Colonies may have several functional queens. Winged reproductives emerge from April to June. Flights from the nest usually occur before dawn on still, moonless nights; the exit of males and females from the colony may last for several weeks.

The interior of the nest may extend 6 m, and it may occupy 420 m2, and have 1000 entrance holes. Colonies may occupy the same nest site for more than 50 years. The interior of the nest contains chambers for growing a fungus on macerated plant material, primarily leaves. Adults and larvae eat the fungus. Minor workers cultivate the fungus and care for the brood larvae, medium-sized workers cut and transport the leaves and other plant material, and large workers guard the nest. Workers forage 90-180 m from the nest site and make conspicuous paths. During summer, they forage at night, but in other seasons they forage during the day. Workers also collect floral parts, seeds, caterpillar droppings, and other plant material. Indoors they forage for rice, meat, sugar, and bread. This species is native to North America, and itoccurs in eastern Texas and western Louisiana, and south into Mexico.

Camponotus

This is the largest ant genus, with about 1000 species worldwide, distributed in tropical and temperate regions. They are called carpenter ants because of the habit of some species to excavate nestgalleries in wood. Carpenterantsdonoteatwood. Many species in this genus do not nest in wood, but live in soil or plants. In North America, there are 23 species of Camponotus that are considered structural or nuisance pests, but only seven of these species cause severe damage to structural timbers. The others invade houses and other buildings and forage for food; they excavate wood, but the damage is limited. Workers are generalized scavengers on a variety of animal materials in natural and domestic habitats. They are typically established in small or large colonies, and sometimes colonies are divided into a parent and several satellite nests.

Pest status of carpenter ants is based on the damage by some species to live in standing trees in managed forests in the natural environment, and the structural damage and household nuisance of the several species in the urban environment. In north temperate regions, such as northern USA and southern Canada, carpenter ants replace subterranean termites as the most important wood-infesting insect in the urban environment. Camponotus infestations cause millions of dollars in repair, replacement, and control costs in the USA and Canada.

In Europe, C. herculeanus causes the most damage to structures, and the value may be comparable to the amounts in the USA.

Adult Camponotus are 3-14 mm long, and may be all black, black and red, or reddish brown. Antennae are 12-segmented and without a club. The antennal scape is inserted some distance from the clypeal border, and this feature distinguishes the Camponotus from Lasius and Formica. Maxillary palps are six-segmented, labial palps are four-segmented, and ocelli are absent. The epinotum lacks spines and the abdominal pedicel is one-segmented. Large workers have heads disproportionately larger than those of small workers; these large, big-headed individuals are called major workers, and the small ones are called minor workers. The proportion oflarge workers (majors) in the colony is an indication of its age. The percentage of major workers is high in old colonies and low in young colonies.

Nests are in live or dead trees, in rotting logs or stumps, or in sound or moisture-damaged structural wood. Some species nest in soil beneath logs and leaf litter, such as C. floridanus. Workers excavate wood with their large mandibles; the fibrous shavings are removed and pushed out of the galleries through the opening, or packed into unused tunnels. Galleries are irregular in shape and are generally excavated in the direction of the wood grain, and in the sapwood portion of the wood. Walls of the galleries are smooth and have a sandpapered appearance. Part of nests may occur in soil, but these often serve as incubation sites for brood, and the actual nest may be adjacent to these soil chambers in roots or wood. Trees utilized for nest sites in Europe and Canada include the softwood species of fir Abies and spruce (Picea); in the Pacific northwest of the USA, western red cedar and Douglas fir are most often attacked by C. modoc. The main colony is usually in the base of the tree, and galleries extend into the roots and up the trunk.

Colonies are usually large and divided into small satellites and a main nest site with the parent colony. The parent colony is usually in a humid environment and contains the functional queens and developing brood, including the eggs and small larvae. In the satellites there are only workers, full-grown larvae, pupae, and sometimes winged reproductives; satellite colonies may be located in dry and warm locations. Colonies maintain contact with one another by movement of brood and workers along interconnecting pathways, which may be on the surface or in the soil. During winter, contact between the colony segments usually stops, but is re-established in spring. The number of satellite nests per colony is variable, and probably linked to species, environmental conditions, and colony age. Colonies of C. herculeanus and C. noveboracensis may have 8-13

satellites, 10 satellites for C.floridanus, while five satellites have been reported for C. modoc and C. vicinus.

The size and age of the colony when winged reproductives are produced are variable, and these features are difficult to determine. Estimates of the total number of workers in a colony when reproductives are produced are: 12 000-50 000 for C. her-culeanus, 8900 for C. noveboracensis, 9000-12 000 for C. modoc, 3018-10243 for C. pennsylvanicus, 2631 for C. chromaiodes (as C.ferrugineus), 150-8100 for C.floridanus, and 50 000 for C. vici-nus. Estimates of colony age when reproductives are produced depend on the development rate of the colony, and whether there are multiple queens. In multiple-queen or polygynous colonies, overall growth is accelerated and reproductives may be produced sooner than in single-queen colonies. Reproductives are produced in C. modoc and C. vicinus colonies after a minimum of 10 years, and for C. pennsylvanicus it may take 3-5 years. Winged forms produced the preceding summer and overwintered in the nest usually leave to mate in the spring. There may be several mating flights, some with a large number of individuals and some with only a small number. They usually occur in the late afternoon of sunny, warm, and humid days.

Following mating, males die and queens seek a sheltered site to deposit a batch of 9-16 eggs over a period of 2-3 days; hatching is in 2-3 weeks. Small larvae are covered in fine setae with hooked tips. When larvae are stacked, the hooked setae interlock and clusters of larvae can be moved together by the queen or workers. The queen and the first batch oflarvae are nourished by the metabolism of her fat bodies and flight muscles. Workers produced from the first brood are small (minor workers) and show little size variation. Colony growth with a founding queen is slow. When the first brood enters the pre-pupal stage in late summer, eggs for the second brood are laid. In fall, colony activities decrease and the parent and satellite segments of the colony enter a dormant phase to overwinter. After the first year, two periods of oviposition and larval development occur in colonies. Camponotus workers are polymorphic, and the food supply determines worker size. Major workers are not produced until the third season in colonies of C. pennsylvanicus, C. chromaiodes, and C. modoc.

Natural food includes honeydew, plant exudates, and live and dead insects and other arthropods. They also scavenge on the carcasses of dead vertebrates. Indoors they forage for sweets and high-protein foods. During spring and early summer, when brood production is at a peak, the workers prefer proteins, which are fed to developing larvae. In late summer and fall, workers prefer carbohydrates, which are used as energy sources by adults. In nonforested areas, carpenter ants follow chemical and physical trails on the ground. In forested areas, they often construct extensive tunnel systems through the soil litter. The majority of foraging is done at night. The peak foraging activity period for C. modoc is 20:00-4:00 h in the Pacific northwest. In California, foragers are active all day from May to October, but switch to nocturnal foraging in July and August. Foraging by C. pennsylvanicus may be influenced by ambient humidity and temperature may be important in June and August, whereas time of day is a determining factor in July.

Most species of carpenter ants are nocturnal foragers and rely on chemical trails for orientation to and from the nest to a food source. A trail pheromone, produced in the hindgut, is deposited by touching the tip of the abdomen to the ground as the workers move along the established trail. They also use a light compass and orient to the sun, the moon, or streetlights at night. They also orient to landmarks such as trees, bushes, and rocks; the silhouette of a tree against the night sky may be sufficient to determine the way to the nest. Indoors, carpenter ants orient to artificial pathways formed by electrical wires and waterpipes. On the outside of structures, they often travel along the branches of trees that contact the roof or siding.

Infestations indoors are usually satellite nests and they are connected to a main colony which is located outdoors in a living or partially dead tree, woodpile, or some other wood structure. Primary or satellite nests may be in roof timbers and remain unnoticed for many years because workers forage outdoors and primarily in the evening. However, nests may be established in wall voids, and the ants observed or heard during the day or evening, or winged swarmers observed at windows. The most frequent locations of nest sites in structures include exterior and interior wall voids, in the attic or other roofsupports, in subflooring, in ceiling joists, and the sill plate or foundation piers. Chewing sounds made by large-headed workers tunneling in the wood and the rustling sounds ofnumerous workers moving in galleries can be heard 2-3 m away, especially at nightwhen houses may be quiet and the ants are active. When disturbed by a knock on the wall near the nest, workers of C. modoc will often respond by striking walls of their tunnels with their mandibles and gasters, apparently to alert the colony.

The fibrous pieces of wood (frass) resulting from carpenter ant tunneling in wood are concentrated in unused galleries or mixed with other colony debris and pushed out of the nest through small openings (windows) to form small piles. Some colonies deposit frass several meters from the nest site.

Figure 9.4 Hymenoptera: Formicidae. (a) Camponotus floridanus; (b) C. caryae; (c) C. castaneus; (d) C. chromaoides; (e) C. nearcticus; (f) C. pennsyluanicus, (g) C. marginatus decipiens; (h) C. tortuganus.

The fibrous pieces of wood removed by the workers are about 3-5 mm long and the color depends on the condition of the wood. Tunneling in sound wood produces frass uniform in color; frass from moisture-damaged wood may be a mix of dark and light pieces. Carpenter ant frass also contains ant feces, small pieces of soil and gravel, and leftover pieces offood, such as seed coats and uneaten parts of insects, and parts of dead carpenter ants.

Camponotus castaneus (Fig. 9.4c) Workers are 7-10 mm long, the body is shiny, and the color ranges from yellowish brown to yellowish red. The head and gaster are usually darker than the thorax. The head is as long as or longer than wide. Cheeks are without erect setae. The scape extends beyond the posterior margin of the head. The middle and hind tibia each have a row of graduated bristles. Colonies have 200-1000 individuals, and probably one functional queen. Workers forage at night, and occur indoors. This species is native to North America, and occurs from Iowa to New York, south to Texas and Florida.

Red carpenter ant, Camponotus chromaiodes (= C. ferrugineus) (Fig. 9.4d) Workers are 6-13 mm long; the head and most of the gaster are blackish brown to black. The thorax, pedicel, and base of the gaster are reddish brown. Setae on the gaster are golden or pale yellow. Near the apex of each middle and hind tibia there is a short row of graduated bristles. Nests are usually in wooded areas and established in dead standing trees, rotted logs, and stumps, and the galleries often extend into the soil. Indoor nests are excavated in moisture-damaged wood. Colonies have one queen and about3000 workers when mature, producing winged females and males. Natural food is live and dead insects, and honeydew; they are not common indoors. This species is native to North America, and occurs from Nebraska to New York, south to Georgia. In 1798, Fabricius described this ant as Formica ferruginea. However, that name is a homonym of F. ferruginea, which was described earlier (1791). This species was moved to Camponotus by Roger in 1863, and the replacement name, C. chromaiodes, was provided by Bolton in 1995.

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