Pseudacteon tricuspis

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Pseudacteon tricuspis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Phoridae
Genus: Pseudacteon
Species:
P. tricuspis
Binomial name
Pseudacteon tricuspis
Borgmeier, 1925

Pseudacteon tricuspis (commonly referred to as a phorid fly or fire ant decapitating fly) is a parasitic phorid fly that decapitates its host, the imported Solenopsis invicta fire ant. [1] There are over 70 described species within the Pseudacteon genus, which parasitize a variety of ant species. However, P. tricuspis is very specific to its host ant and will not attack other native ant species, making it a good biological control against the fire ant. P. tricuspis was also introduced into the United States for this purpose. Aside from the United States, P. tricuspis has also been found in South America, Europe, and Asia. Female P. tricuspis deposit their eggs directly into the fire ant host. Deposition into the ant host determines the sex of the egg, which grows within the host until adulthood, killing and decapitating the host in the process. Interestingly, P. tricuspis has a male-biased sex ratio, where the males are smaller than the females.

Contents

Description

Pseudacteon tricuspis is a species of the Pseudateon genus and a member of the family Phoridae , which is commonly called scuttle flies, humped-back flies, and phorid flies. [2] Eight native Pseudacteon species parasitize native fire ants in the United States (Plowes 2009).

The adult P. tricuspis flies are 0.9-1.5mm in length. [3] The mandibles of the larvae are unable to chew or digest food and are instead used to aid in movement and anchoring within the host. [4] The ovipositor, which is the organ that is used by the female to lay eggs, looks different in all species within the Pseudacteon genus and can be used to distinguish the species from one another.

Distribution

Pseudacteon tricuspis is widely distributed around Argentina, Brazil, and other parts of South America, Europe, and Asia. About two dozen species of the genus parasitize native fire ants in South America. [2] Since its introduction to the United States, the species can be found across the country, but is concentrated along the south east parts, including Florida, Alabama, Arkansas, and Louisiana. [5]

Habitat

Solenopsis invicta, host of P. tricuspis Solenopsis invicta casent0005804 profile 1.jpg
Solenopsis invicta, host of P. tricuspis

Pseudacteon tricuspis is predominantly found within the natural range of where the host Solenopsis invicta fire ant can be found. Climates range from rain forests to swamps to dry areas. They are not preferential to any sort of habitat, partially because P. tricuspis live the majority of their lives within the host. P. tricuspis is not known to be attracted in large groups to anything but the host ant.

Life history

Pseudacteon tricuspis will spend a majority of its life cycle within the host ant, even after the host dies. Development time from egg deposition to mature adult is 5 to 12 weeks, depending on temperature (with increased longevity at lower temperatures). Sex determination is dependent on the size of the host ant that the egg is deposited within. The female flies have a greater average fitness if they are using larger host fire ants. However, the exact mechanism of how this sex determination occurs is unknown. [3]

Egg

The eggs of the fly are approximately 130 μm long by 20 μm wide. [2] They have the shape of a torpedo and are injected into the thorax of the worker fire ant by the mother. [3] The egg usually takes around 4–5 days to finish embryonic development and hatch. [4]

Larvae

The fly hatches from the egg in the first instar and will usually shed their serosa within 24 hours, although the process has been recorded to last up to 20 days. By day four the second instar typically will have situated itself fully within the ant's head. [4] During both the second and third instar the fly maggot relies heavily on ant hemolymph for nutrition. During this time, the host fire ant appears and behaves normally because the parasite fly does not consume tissue. The third instar will then release an enzyme or hormone that will loosen and decapitate the head of the host ant, which the fly then eats and resides inside. [3]

Pupae

The pupae are opaque and have a pale color. [2] The fly will stay inside the head capsule and grow, filling the shape of the host’s head capsule. [4] The females will have developed fully formed wings. Pupal development takes around 2–6 weeks, dependent on temperature. [3]

Adult

When the adult fly is fully grown, emergence from the host fly takes only a few seconds in total and are ready to mate and lay eggs within the next few hours. The adult lifespan is only 3 to 5 days. [3]

Food resources

The flies use fire ants' semiochemicals to locate the fire ant species Solenopsis invicta and can do so from up to 50 meters away. [1] While other species within the Pseudacteon genus have been found to be generalists and feed on a wide range of resources, in the field the P. tricuspis fly will only feed on its host. However, research in laboratories has found that feeding the fly sugar has a significant effect on increasing the lifespan of the fly, with longevity increasing by a factor of 2 to 3. In the field, the parasites could potentially obtain sugar from nectar or honeydew, but provision of supplemental sugar sources around release sites of the fly may improve the success rate of the fly as a control for the fire ant. [6]

Mating

Males have a long sensilla subtype within their antennae that is absent in the females. While its purpose is not completely clear, it is thought to detect female odors, such as sex pheromones, during mate search. [1] Both sexes are also attracted to the odor of the host fire ant and mating occurs while the females are looking for suitable hosts. Females will track the movement and the behavior of the fire ant hosts while males will hover and spin around in the air looking for females. After locating one, the male will grab onto the female, and copulation takes less than a second. During this process, neither sex is able to keep flying, causing both to drop to the ground. Both the males and females of P. tricuspis will mate several times. The female P. tricuspis may produce from 100 to 300 eggs during its short mating time, but will only insert a single egg into each worker ant. [3]

Sexual dimorphism

The species has sexual dimorphism, with the females being much larger than the males. [5] This is likely occurs because of the females being aggressive and fighting with other females over depositing their own eggs within a host. The females fight over the larger host ants to deposit their eggs in as these eggs will have a larger chance of survival. Larger females will most likely win these fights, leading to females growing larger than males.

Sex ratio

The species typically has a sex ratio that is biased towards males (usually in a 2:1 ratio). This is attributed to the relative size of the host ants, which happen to have more large individuals than smaller individuals. There is a lower number of hosts that can support the development of female flies, making the female gender rarer. This creates intraspecific competition between the P. tricuspis females who compete with each other in trying to oviposit within the same host. The females exhibit aggressive and territorial behavior. [5]

Attack

The fly participates in attacking behavior of the Solenopsis invicta fire ant when attempting to oviposit. The adult female flies will hover around 3 to 5mm above their chosen host ant and orient their ovipositor towards the host. They will then quickly dive in and inject the egg into the thorax of the worker host. The fly will avoid attempting to oviposit in the alates of the colony and will instead exclusively attack worker ants. Successful egg deposition only occurs around 8-35% of the time. [3]

Activity

The daily activity of the P. tricuspis fly starts very low in the early morning, increases gradually, then peaks at midday. Maximum male emergence has been seen to occur around one hour before maximum female emergence. In terms of seasonal activity, the fly population is seen throughout the year, but are highest in the fall and summer and lowest in the winter and spring. This correlates to a density dependent response to the availability of the fire ant host, which is greater in the fall due to the frequent rainfall. [7]

Biological control

Pseudacteon tricuspis was the first species of Pseudacteon fly successfully used as a biological control agent for imported red fire ant in the US. [2] Imported red fire ant Solenopsis invicta was accidentally introduced into the United States in Alabama in the 1930s. Since then, its populated area has expanded across the country, including California. The ants are extremely detrimental to the environment of the United States, costing around a billion dollars every year in damage and impacting native fauna and habitats. While chemical pesticides have been tested as a way of controlling the ants, the solution is not environmentally or financially sustainable. Between the summer of 1997 and fall of 1999, the P. tricuspis fly was released in eight different sites over the mounds of the fire ant located throughout North Florida as a self-sustained way of controlling the fire ant, with six of these sites having a survival population after the first winter. Over the years, the population of P. tricuspis fly at these sites continued to grow and expanded beyond the area of the release sites, and in the fall of 2000 the sites fused into one large occupied area. The purpose of the P. tricuspis fly was to stress the fire ant population in order to shift the balance back in favor of the native ants in America. [8] While the exact impact of the fly on the fire ant population is unknown, the fire ant has evolved to develop specific defense mechanisms against the fly, indicating that there is some sort of large population wide significance on the survival of the fire ant colonies. [3] Additionally, in the presence and attack of the P. tricuspis, the fire ant will typically decline its foraging and resource retrieval rates significantly, by almost 84%. [7]

Related Research Articles

<span class="mw-page-title-main">Fly</span> Order of insects

Flies are insects of the order Diptera, the name being derived from the Greek δι- di- "two", and πτερόν pteron "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced mechanosensory organs known as halteres, which act as high-speed sensors of rotational movement and allow dipterans to perform advanced aerobatics. Diptera is a large order containing an estimated 1,000,000 species including horse-flies, crane flies, hoverflies, mosquitoes and others, although only about 125,000 species have been described.

<span class="mw-page-title-main">Fire ant</span> Genus of red ants

Fire ants are several species of ants in the genus Solenopsis, which includes over 200 species. Solenopsis are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many of the names shared by this genus are often used interchangeably to refer to other species of ant, such as the term red ant, mostly because of their similar coloration despite not being in the genus Solenopsis. Both Myrmica rubra and Pogonomyrmex barbatus are common examples of non-Solenopsis ants being termed red ants.

<span class="mw-page-title-main">Red imported fire ant</span> Invasive ant species

Solenopsis invicta, the fire ant, or red imported fire ant (RIFA), is a species of ant native to South America. A member of the genus Solenopsis in the subfamily Myrmicinae, it was described by Swiss entomologist Felix Santschi as a variant of S. saevissima in 1916. Its current specific name invicta was given to the ant in 1972 as a separate species. However, the variant and species were the same ant, and the name was preserved due to its wide use. Though South American in origin, the red imported fire ant has been accidentally introduced in Australia, New Zealand, several Asian and Caribbean countries, Europe and the United States. The red imported fire ant is polymorphic, as workers appear in different shapes and sizes. The ant's colours are red and somewhat yellowish with a brown or black gaster, but males are completely black. Red imported fire ants are dominant in altered areas and live in a wide variety of habitats. They can be found in rainforests, disturbed areas, deserts, grasslands, alongside roads and buildings, and in electrical equipment. Colonies form large mounds constructed from soil with no visible entrances because foraging tunnels are built and workers emerge far away from the nest.

<span class="mw-page-title-main">Phoridae</span> Family of flies

The Phoridae are a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking to the wing. This behaviour is a source of one of their alternate names, scuttle fly. Another vernacular name, coffin fly, refers to Conicera tibialis. About 4,000 species are known in 230 genera. The most well-known species is cosmopolitan Megaselia scalaris. At 0.4 mm in length, the world's smallest fly is the phorid Euryplatea nanaknihali.

<span class="mw-page-title-main">Eucharitidae</span> Family of wasps

The Eucharitidae are a family of parasitic wasps. Eucharitid wasps are members of the superfamily Chalcidoidea and consist of three subfamilies: Oraseminae, Eucharitinae, and Gollumiellinae. Most of the 55 genera and 417 species of Eucharitidae are members of the subfamilies Oraseminae and Eucharitinae, and are found in tropical regions of the world.

<i>Megaselia scalaris</i> Species of fly

The fly Megaselia scalaris is a member of the order Diptera and the family Phoridae, and it is widely distributed in warm regions of the world. The family members are commonly known as the "humpbacked fly", the "coffin fly", and the "scuttle fly". The name "scuttle fly" derives from the jerky, short bursts of running, characteristic to the adult fly. The name "coffin fly" is due to their being found in coffins, digging six feet deep in order to reach buried corpses. It is one of the more common species found within the family Phoridae; more than 370 species have been identified within North America.

<i>Phormia regina</i> Species of fly

Phormia regina, the black blow fly, belongs to the blow fly family Calliphoridae and was first described by Johann Wilhelm Meigen.

Rhagoletis juglandis, also known as the walnut husk fly, is a species of tephritid or fruit fly in the family Tephritidae. It is closely related to the walnut husk maggot Rhagoletis suavis. This species of fly belongs to the R. suavis group, which has a natural history consistent with allopatric speciation. The flies belonging to this group are morphologically distinguishable.

<i>Solenopsis saevissima</i> Species of ant

Solenopsis saevissima, commonly known in Brazil as formiga de fogo, formiga-vermelha, or formiga-lava-pes, is one of more than 185 species in the genus Solenopsis. It, along with 13 other species, is also a member of the Solenopsis saevissima species group which are popularly known as fire ants.

<i>Apocephalus borealis</i> Species of fly

Apocephalus borealis is a species of North American parasitoid phorid fly that attacks bumblebees, honey bees, and paper wasps. This parasitoid's genus Apocephalus is best known for the "decapitating flies" that attack a variety of ant species, though A. borealis attacks and alters the behavior of bees and wasps. These flies are colloquially known as zombie flies and the bees they infect are colloquially known as zombees. Association with honey bees has so far only been documented from California, South Dakota, Oregon, Washington, British Columbia, and Vermont.

<span class="mw-page-title-main">Metopininae</span> Subfamily of flies

The Metopininae are a subfamily of flies in the family Phoridae.

Diptera is an order of winged insects commonly known as flies. Diptera, which are one of the most successful groups of organisms on Earth, are very diverse biologically. None are truly marine but they occupy virtually every terrestrial niche. Many have co-evolved in association with plants and animals. The Diptera are a very significant group in the decomposition and degeneration of plant and animal matter, are instrumental in the breakdown and release of nutrients back into the soil, and whose larvae supplement the diet of higher agrarian organisms. They are also an important component in food chains.

<i>Paracantha gentilis</i> Species of fly

Paracantha gentilis is a species of tephritid or fruit fly in the genus Paracantha of the family Tephritidae. It has a widespread distribution throughout the Western United States, and has also been found as far south as Mexico and Costa Rica. It most closely resembles Paracantha culta, which is widespread in the Southeastern United States, but P. gentilis can be distinguished by having smaller spots on the head.

<i>Pseudacteon</i> Genus of flies

Pseudacteon is a genus of flies in the family Phoridae. There are over 70 described species of Pseudacteon fly. They are also known as ant-decapitating flies due to their parasitic larval stage. An egg is injected by the female fly into the shoulder joint of an ant worker. Soon after, the egg undergoes rapid inflation as it appears to absorb ant hemolymph. This first instar larva migrates into the ant head and consumes the jaw muscle and other tissues, leaving the mandibles hanging and preparing a future exit space. After about two weeks, the ant worker is termed a "zombie" because the fly larva has effectively taken control. The worker leaves the nest and dies in the leaf litter or in a crack in the soil. As it dies, the ant's head falls off, apparently because the fly larva releases an enzyme that dissolves the membrane attaching the ant's head to its body. The fly pupates in the detached head capsule, requiring a further two weeks before emerging through the ant's mouth. In tropical, subtropical areas the flies are active all year round, but in temperate regions they are active during all months except the winter months. Several Pseudacteon species were deliberately introduced to the United States to combat via biological control the invasive fire ant species Solenopsis invicta.

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Exorista mella is a tachinid fly of the genus Ezorista within the family Tachinidae of the order Diptera. They are typically found in the United States and Canada. Within the U.S in the state of Arizona they have been found in both mountainous and agricultural regions. E. mella is a parasitoid fly, a polyphagous generalist which parasitizes a variety of hosts.

<i>Apocephalus paraponerae</i> Species of fly

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<span class="mw-page-title-main">Metopinini</span> Tribe of flies

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Microselia is a genus of flies in the family Phoridae.

References

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  7. 1 2 Henne, Donald Charles, 1968- author. Population ecology of Pseudacteon tricuspis borgmeier (Diptera: phoridae), an introduced parasitoid of the red imported fire ant Solenopsis invicta buren (Hymenoptera: formicidae) in Louisiana. OCLC   1101100726.{{cite book}}: |last= has generic name (help)CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
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