Mallophora ruficauda

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Mallophora ruficauda
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Asilidae
Genus: Mallophora
Species:
M. ruficauda
Binomial name
Mallophora ruficauda
Wied., 1828

Mallophora ruficauda is a species of parasitic robber fly in the family Asilidae, endemic to South and Central America. [1] Like other robber flies, M. ruficauda is known for its aggressive behavior and predation upon other insects, especially bees. M. ruficauda (like other members of the genus Mallophora) mimics a bumblebee to fool predators into thinking it has a painful sting and is not worth eating. [2]

Contents

M. ruficauda larvae parasitize scarab beetles and likely serve as an important biocontrol for the beetles, a pest species that eats the roots and tubers of plants while in the larval stage. On the other hand, adult M. ruficauda are apicultural pests because they feed on worker honeybees.

Description

M. ruficauda is a bumblebee mimic, meaning it appears very similar to a bumblebee despite actually being a fly. It is large and covered in dense black hair (setae) with a patch of yellow on the thorax, and has a pointed black abdomen with a spot of reddish hair at the tip. The wings are smoky brown and generate a buzzing sound during flight, similar to the wings of bees. The head is black and the face is covered in white hairs, which are also found on the ventral side of the femora, tibia, and tarsale of the third pair of legs in males. The third pair of legs is stronger and lengthened compared to the other two smaller pairs. [3]

Larvae are minute, measuring only 1.35 mm in length and 0.32 mm in width on average. [4] Their small size allows them to easily disperse by wind after hatching.

M. ruficauda is endemic to South and Central America, and is primarily present in the open grasslands and meadows where it lays its eggs. [5] The flies are most active during the day, especially during sunny and hot days in the summer (December-May in the Southern Hemisphere). [3]

Sensory physiology

Researchers have shown that M. ruficauda antennae are involved in resource-searching behavior, in addition to detecting outside chemical cues that the flies are able to pick up on. [6] Their antennae are composed of four different segments: the scape, pedicel, postpedicel, and style. In addition, there are three separate types of sensory pits observed on the antennae. [6] Together, these morphological characteristics contribute to the odor detection mechanism found in adult M. ruficauda, which may be used in mate detection, habitat recognition, predator avoidance, and searching for food. [6]

Life history

Larval stage

Eggs are laid in aggregate clusters of approximately 300 on the tips of tall stalks of grass or wire fencing. Oviposition occurs at the optimal height for larval dispersal and location of hosts, which is about 1.25 to 1.5 meters above the ground. [7] [4] These clusters are typically near adult food sources, such as beehives. Upon hatching, the tiny larvae drift to the ground, dispersing under wind power. This helps them spread out so that they do not all encounter and parasitize the same host, which would cause competition for resources between the larvae. [4] The larvae then begin to dig in an attempt to find a host (preferably a larval Cyclocephala signaticollis, a type of scarab beetle, though the larvae are not strict specialists and will parasitize several species of white grub), [8] which will be located by the chemical cues provided by its own abdominal excretions. The larvae take 7 days to molt in the soil and enter the second instar, at which point they can detect and orientate towards the chemical cues produced by the grubs, and they dig through the soil towards prospective hosts. [9] Upon finding a host, the larvae attach to the cuticle and begin to feed. The larvae stay attached to their hosts for the rest of the larval stage, eventually killing the host upon pupation. Larvae can survive through the second instar on their own, but if they do not find a host before the second instar ends, they will die. [10]

Larval superparasitism

Superparasitism is common among the larvae of M. ruficauda, with many larvae sometimes infecting a single host. They prefer unparasitized hosts if they can find them in order to avoid competing with members of their own species. However, the hosts are randomly distributed in the soil and the larvae may all have to share a host if only one is available. The larvae can discriminate between unparasitized and already-parasitized hosts by chemical cues, and will preferentially crawl towards unparasitized grubs. As the size of a host increases, the likelihood and severity of superparasitism also increases (presumably because a larger host is capable of supporting more parasites). These findings are one of the first reports of host discrimination by larvae rather than by adults. It makes sense that a Dipteran species would evolve this ability, since Dipteran parasitoids rarely have a strong enough ovipositor to lay eggs directly in a host. This eliminates the ability of the mother to choose a good host for her offspring; instead, the larvae have to find a host for themselves once they hatch. Therefore, they should be able to determine host quality. However, they are unable to detect free-living individuals of their own species, suggesting that they do not have significant interactions with them beyond competition for hosts. [11]

Host defense

Researchers have explored many mechanisms that protect different hosts from the parasitic behavior of M. ruficauda. Hosts seem to display defense mechanisms both before and after parasitism. [12] In certain cases, the hosts can escape M. ruficauda parasitism some weeks after the original attack. Violent body movements and torsion away from the parasite seem to be some of the most effective behavioral responses that allow for evasion of M. ruficauda. [12] In addition, some studies have suggested that high environmental temperatures increase the probability that the host will successfully kill its parasitoid. [12] M. ruficauda may prefer Cyclocephala in particular because these beetles have a relatively low behavioral reaction to simulated parasitoid attacks; their poor immunological defense strategies make them an easier target for the larvae. [12]

Adult life

Upon pupating, the larva kills its host grub. The adult fly leaves the pupa and emerges from the soil about 2 months after the eggs first hatched, and begins to prey upon bees and other insects. [13]

Food resources

Larvae exclusively feed on their white grub hosts until they pupate and emerge as full-grown adults. [14] The adults are predatory, feeding on insects (primarily Hymenoptera but also other insects, including other members of Diptera) endemic to the meadows that they inhabit. [15]

Mating

During the mating season, females spend most of their time resting on twigs, while males patrol fixed routes in search of mates. If a male fly finds a female, the male initiates a long courtship dance. The male positions itself perpendicular to the female, then rotates the third pair of legs in order to position them upwards and posteriorly. The male fly will then rhythmically twitch the third legs in bursts, alternating with periods of hovering. If the male touches the female's wings during this display, the female responds by rapidly scissoring them back and forth. This courtship takes approximately 30–40 minutes, after which copulation finally occurs (unless the female flees at any point during the dance, in which case the courtship fails). Alternatively, another male may intervene to compete for the female's attention, which may result in a fight between the two males. The female's signal to the male that she accepts him is subtle and still not understood; unless she flies away, she remains motionless throughout most of the courtship other than the occasional movements of her wings. [3]

Parental care

Host grubs are hidden in the soil, so mother flies cannot predict where they will be and lay her eggs in exactly the right spot. [16] Instead, gravid flies lay their eggs at the optimal height on tall plants or wire fences in their meadow habitats. At around 1.25 to 1.5 meters off the ground, the larvae will gain the greatest benefit from the wind helping them to disperse. This results in the maximum number of offspring finding a host, with the minimum number of offspring being forced to share a host. [4]

Mimicry

Like several other species in the genus Mallophora, M. ruficauda is a bumblebee mimic, possibly as a result of Batesian mimicry, a type of mimicry in which a palatable or edible organism (such as the fly, which cannot sting) imitates an unpalatable organism (such as a bumblebee with a painful sting). [17] This prevents predation, as predators will interpret the fly as an inedible bee and will not attempt to eat it. The flies are large and plump, covered in black and yellow fuzzy hair, and buzz like bees do during flight. [18]

Importance to humans

M. ruficauda is an important agricultural pest, particularly in the Pampas region of Argentina where honey is farmed. [10] The adults kill and eat honeybees as one of their primary food sources, causing losses for farmers. Members of the genus Mallophora across the Americas cause problems for beekeepers by killing their honeybees, which have become one of their preferred foods even though these bees are not native to the region. During years when the density of M. ruficauda is high, they can cause up to 80% losses of honey production in regions where they are endemic. [19]

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">Parasitoid</span> Organism that lives with its host and kills it

In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasitism, distinguished by the fatal prognosis for the host, which makes the strategy close to predation.

<span class="mw-page-title-main">Tachinidae</span> Family of insects

The Tachinidae are a large and variable family of true flies within the insect order Diptera, with more than 8,200 known species and many more to be discovered. Over 1,300 species have been described in North America alone. Insects in this family commonly are called tachinid flies or simply tachinids. As far as is known, they all are protelean parasitoids, or occasionally parasites, of arthropods, usually other insects. The family is known from many habitats in all zoogeographical regions and is especially diverse in South America.

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

The Bombyliidae are a family of flies, commonly known as bee flies. Adults generally feed on nectar and pollen, some being important pollinators. Larvae are mostly parasitoids of other insects.

<span class="mw-page-title-main">Kleptoparasitism</span> Type of animal feeding strategy

Kleptoparasitism is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct feeding, such as when food is scarce or when victims are abundant. Many kleptoparasites are arthropods, especially bees and wasps, but including some true flies, dung beetles, bugs, and spiders. Cuckoo bees are specialized kleptoparasites which lay their eggs either on the pollen masses made by other bees, or on the insect hosts of parasitoid wasps. They are an instance of Emery's rule, which states that insect social parasites tend to be closely related to their hosts. The behavior occurs, too, in vertebrates including birds such as skuas, which persistently chase other seabirds until they disgorge their food, and carnivorous mammals such as spotted hyenas and lions. Other species opportunistically indulge in kleptoparasitism.

<span class="mw-page-title-main">Asiloidea</span> Superfamily of flies

The Asiloidea comprise a very large superfamily insects in the order Diptera, the true flies. It has a cosmopolitan distribution, occurring worldwide. It includes the family Bombyliidae, the bee flies, which are parasitoids, and the Asilidae, the robber flies, which are predators of other insects.

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

The Conopidae, also known as the thick-headed flies, are a family of flies within the Brachycera suborder of Diptera, and the sole member of the superfamily Conopoidea. Flies of the family Conopidae are distributed worldwide in all the biogeographic realms except for the poles and many of the Pacific islands. About 800 species in 47 genera are described worldwide, about 70 of which are found in North America. The majority of conopids are black and yellow, or black and white, and often strikingly resemble wasps, bees, or flies of the family Syrphidae, themselves notable bee mimics. A conopid is most frequently found at flowers, feeding on nectar with its proboscis, which is often long.

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

The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their expert predatory habits; they feed mainly or exclusively on other insects and, as a rule, they wait in ambush and catch their prey in flight.

<i>Hermetia illucens</i> Common and widespread fly of the family Stratiomyidae

Hermetia illucens, the black soldier fly, is a common and widespread fly of the family Stratiomyidae. Since the late 20th century, H. illucens has increasingly been gaining attention because of its usefulness for recycling organic waste and generating animal feed.

<i>Bombylius major</i> Species of fly

Bombylius major is a parasitic bee mimic fly. B. major is the most common type of fly within the Bombylius genus. The fly derives its name from its close resemblance to bumblebees and are often mistaken for them.

<i>Bombus pensylvanicus</i> Species of bee

Bombus pensylvanicus, the American bumblebee, is a threatened species of bumblebee native to North America. It occurs in eastern Canada, throughout much of the Eastern United States, and much of Mexico.

<i>Phytomyza ilicis</i> Species of insect

Phytomyza ilicis, the holly leaf miner, is a leaf mining fly in the family Agromyzidae, whose larvae burrow into leaves of the holly tree leaving characteristic pale trails or leaf mines.

<i>Compsilura concinnata</i> Species of fly

Compsilura concinnata is a parasitoid native to Europe that was introduced to North America in 1906 to control the population of an exotic forest, univoltine, spongy moth named Lymantria dispar. It is an endoparasitoid of larvae and lives with its host for most of its life. Eventually the parasitoid ends up killing the host and occasionally eating it. It attacks over 200 host species, mainly insects from the Orders: Coleoptera, Lepidoptera and Hymenoptera. Since this parasite has the ability to attack many different types of hosts, the organism has spilled over from the intended forest systems into other areas, like agricultural fields, affecting cabbage pests including the cabbage looper (Trichoplusia); the cabbage worm ; and even other invasive species such as the brown-tail moth. However, it also attacks native, non-pest insects such as the Cecropia moth and American moon moth.

<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.

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>Cyclocephala</i> Genus of beetles

Cyclocephala is a genus of scarab beetles from the subfamily Dynastinae. Beetles of this genus occur from southeastern Canada to Argentina, India and the West Indies.

<i>Bombylius canescens</i> Species of fly

Bombylius canescens, is a species of bee-fly belonging to the family Bombyliidae.

<i>Physocephala tibialis</i> Species of fly

Physocephala tibialis is a species of thick-headed fly found throughout the eastern United States, often near flowering plants. The adult fly is primarily black with a yellow face and thin white stripes on the abdomen. It is commonly found along the east coast of the United States and is often found near flowering plants.

<i>Mallophora bomboides</i> Species of fly

Mallophora bomboides, also known as the Florida bee killer, is a predaceous species of robber fly of the family Asilidae that feeds primarily on bumblebees. M. bomboides is a noteworthy instance of Batesian mimicry given its close resemblance to its prey, the bumblebee. These bees are typically found in the Eastern and Southern regions of the United States like South Carolina and Florida.

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.

References

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