''Toxomerus'' is a very large genus of hoverflies. They are found in many parts of North and South America. Most larvae are predators on soft bodied insects, though a few species have been shown to feed on

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

. Adults feed on the pollen of a wide range of flowers.

Morphology

The majority of species are 6–9 mm in length. However, the largest, ''

Toxomerus insignis ''Toxomerus'' is a very large genus of hoverflies. They are found in many parts of North and South America. Most larvae are predators on soft bodied insects, though a few species have been shown to feed on pollen. Adults feed on the pollen ...

'', found throughout the Northeastern part of North America, is 13 mm long. A common trait of species within the genus is their

mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...

of stinging

Hymenoptera Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...

to avoid predators.Penney, Heather D., et al. "The relationship between morphological and behavioral mimicry in hover flies (Diptera: Syrphidae)." ''The American Naturalist'' 183.2 (2013): 281-289. What distinguishes ''Toxomerus'' from other hoverflies is the posterior indentation of their eyes and unique abdominal patterns; the abdominal patterns are diagnostic at the species level within the genus. Eyes are large (taking up approximately 2/3 of head) and range from red to black in color. Males and females can be distinguished by the dorsal spacing of their eyes, with males having a narrow gap and females having more space showing their ocelli.

Classification and distribution

Both molecular and morphological analysis have been used to establish ''Toxomerus'' monophyly. Not all of ''Toxomerus'' species have been described, though over 130 Neotropical species and 6 endemic Nearctic species are known. Some species have been discovered in the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by the ...

in the

afrotropics The Afrotropical realm is one of Earth's eight biogeographic realms. It includes Africa south of the Sahara Desert, the majority of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the island ...

and are assumed to have been introduced due to their high genetic similarity to South American species. ''Toxomerus'' species are the most abundant hoverflies (or syrphid flies) in the Americas. ''

Toxomerus marginatus ''Toxomerus marginatus'', also known as the calligrapher fly, is a common species of hoverfly. It is found in many parts of North America. The larvae are predators of thrips, aphids, and small caterpillars. Adults feed on a wide range of fl ...

'' is the most ubiquitous species in the North and is polyvoltine, brooding multiple times per year. ''

Toxomerus dispar ''Toxomerus'' is a very large genus of hoverflies. They are found in many parts of North and South America. Most larvae are predators on soft bodied insects, though a few species have been shown to feed on pollen. Adults feed on the pollen ...

'' is the most common in the tropics, though '' T. pulchellus'' is more common in some areas.

Biology and ecology

Although they are high fidelity hymenopteran mimics they do not engage in behavioral mimicking such as leg waving, wing wagging, and mock-stinging. They also have significantly less hair than bees. As in all flies, ''Toxomerus'' species have 4 life stages: egg, larva, pupa, adult. The lifespan of the average adult is about a month and can vary depending on the season with shorter spans in the summer and longer in the winter. Mating can occur midair or on the ground depending on species. A female can lay up to hundreds of eggs at a time and will place them where prey or pollen food sources are readily available. They can be found in a wide variety of habitats. Adults can be encountered in dense ground cover including grasses and leaves. Some can do well in urban environments and can be responsible for some pollination in gardens. ''Toxomerus'' larvae are known to typically feed on aphids. Predatory ''Toxomerus'' larvae have also been found to feed on other

Hemiptera Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...

, Acari, and Thysanoptera, along with

Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

larvae. Though ''Toxomerus'' larvae are generally predatory, there are three known exceptions: ''

Toxomerus apegiensis ''Toxomerus'' is a very large genus of hoverflies. They are found in many parts of North and South America. Most larvae are predators on soft bodied insects, though a few species have been shown to feed on pollen. Adults feed on the pollen ...

'', ''

Toxomerus politus ''Toxomerus politus'' is a species of hoverfly (Diptera: Syrphidae). It is known from North, Central and South America. Although little is known about the early stages of this species, associations with corn have been noted. The adults and likel ...

'', and ''

Toxomerus floralis ''Toxomerus floralis'' is a species of syrphid fly Hover flies, also called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of ...

.''''T. politus'' larvae feed on the pollen of ''Zea mays'' (corn), and ''T. apegiensis'' larvae feed on the pollen of ''Olyra obliquifolia'' (bamboo). ''T. floralis'', the larvae of which feed on pollen from ''Cyperus rotundus'' (Java grass) and ''Mitracarpus hirtus'' (tropical girdleweed), is the only species whose larvae are known to feed on plants from different families. Generally, little information is known about the larval biology of ''Toxomerus'' species. Research suggests that other phytophagous ''Toxomerus'' species may be found by searching plants related to rainforest ''Olyra ''species. After the larval stage, ''Toxomerus '' species typically become pollinivorous as adults. Their diets as adults had made some species responsible for pollination in a variety of plant families, including

Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...

, Scrophulariaceae, Ericaceae,

Cyperaceae The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' w ...

, and Orobanchaceae.Kevan, P. G., et al. "Pollination of cranberries, ''Vaccinium macrocarpon'', on cultivated marshes in Ontario." ''Proceedings of the Entomological Society of Ontario''. Vol. 114. 1983.Jordaens, Kurt, et al. "A second New World hoverfly, ''Toxomerus floralis'' (Fabricius)(Diptera: Syrphidae), recorded from the Old World, with description of larval pollen-feeding ecology." ''Zootaxa'' 4044.4 (2015): 567-576. Adults and larvae will forage for pollen during the early daylight hours while their activity drops off at around late afternoon.Dumbardon-Martial, Eddy. "Pollen feeding in the larva of ''Toxomerus pulchellus'' (Diptera, Syrphidae)." ''Bulletin de la Société entomologique de France'' 121.4 (2016): 413-420.

Species

List of ''Toxomerus'' species

References

{{Taxonbar, from=Q2746818 Diptera of North America Diptera of South America Syrphinae Hoverfly genera Taxa named by Pierre-Justin-Marie Macquart