I found this spot eyed hoverfly (Eristalinus species) in my garden resting on a leaf of Caribbean cherry plant (Muntingia species). I photographed this hoverfly using a Canon EOS 80D with Canon EF 100mm f/2.8L Macro IS USM lens, illuminated by Canon MT-24EX macro twin light flash with DIY diffuser.
Hoverflies, sometimes 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 many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods. In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or in ponds and streams. In other species, like this spot eyed hoverfly, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects.
Aphids alone cause tens of millions of dollars of damage to crops worldwide every year; because of this, aphid-eating hoverflies are being recognized as important natural enemies of pests, and potential agents for use in biological control. Some adult syrphid flies are important pollinators.
About 6,000 species in 200 genera have been described. Hoverflies are common throughout the world and can be found on all continents except Antarctica. Hoverflies are harmless to most other animals, despite their mimicry of more dangerous wasps and bees, which wards off predators. This sort of mimicry is called Batesian mimicry. Palatable hoverflies are avoided by predators because they resemble noxious or defended species like wasps and bees. The striking resemblance of many hoverflies to noxious Hymenoptera is a “textbook” example of Batesian mimicry. They are harmless despite their clever mimicry and do not sting.
The size of hoverflies varies depending on the species. Some, like members of the genus Baccha, are small, elongated, and slender, while others, like members of Criorhina, are large, hairy, and yellow and black. As members of the Diptera, all hoverflies have a single functional pair of wings (the hind wings are reduced to balancing organs).
Unlike adults, the maggots of hoverflies feed on a variety of foods; some are saprotrophs, eating decaying plant or animal matter, while others are insectivores, eating aphids, thrips, and other plant-sucking insects. This is beneficial to gardens, as aphids destroy crops, and hoverfly maggots are often used in biological control.
Hoverflies are important pollinators of flowering plants in a variety of ecosystems worldwide. Syrphid flies are frequent flower visitors to a wide range of wild plants, as well as agricultural crops, and are often considered the second-most important group of pollinators after wild bees. However, relatively little research into fly pollinators has been conducted compared with bee species. Bees are thought to be able to carry a greater volume of pollen on their bodies, but hoverflies may be able to compensate for this by making a greater number of flower visits.
Many species of hoverfly larvae prey upon pest insects, including aphids and the leafhoppers, which spread some diseases such as curly top. Therefore, they are seen in biocontrol as a natural means of reducing the levels of pests.
Some pretty amazing studies exist regarding hover flies and their ability to “turn on” and “turn off” their reproductive capabilities based on odours present in the plants. Aphid infested potatoes emit particular odours into the air that attract hover flies and set their egg-laying capability into motion. When no aphids are present, a different odour is released telling the hoverflies there is no prey available. Even in a contained environment, pregnant female hoverflies will not lay eggs on non-infested plants; and, when aphids are present, the number of eggs she lays is hugely dependent on how many aphids are there.