Vinegar flies, also known as fruit flies, pomace flies, or wine flies (all references to the attraction to overripe or rotting fruit that these species demonstrate), are a species of small flies that belong to the family Drosophilidae of the genus Drosophilia. They are not to be confused with the related family Tephritidae; while members of this family are also called “fruit flies” (occasionally “true fruit flies”), they feed primarily on unripe or ripe fruit. Being aware of this distinction is even more important in light of the fact that, in Australia and South Africa, a Mediterranean fruit fly of the family Tephritidae, Ceratitis capitata, is considered to be a serious economic pest.
Description and distribution
Often, the terms “Drosophila” and “fruit fly” are used synonymously with D. Melanogaster (a species of the genus Drosophilia, also known as the common fruit fly). This is the most widespread species, and, as such, the species this article will focus on. However, it is important to know that the entire genus contains more than 1,500 species, which are diverse in appearance, behaviour, and habitat choice.
In North America, you can find approximately 175 species, the most common of which are D. melanogaster, D. busckii, D. funebris, and D. repleta.
As is the case with many insects, the appearance of Drosophilia flies varies with the species they form part of, as well as the source they feed from. Colouring ranges from pale yellow to reddish brown to black, with some species having distinct (usually black) patterns on the wings. They are generally small flies, of around 2-4mm in length, but some (especially many of the Hawaiian species) can grow to be larger than a house fly.
D. Melanogaster flies are yellow-brown, with red eyes and black rings across the abdomen, but with noted differences between males and females. Males have darker backs, with a distinct patch in the abdomen area, as well as sexcombs (a row of dark bristles on the first leg), and a cluster of spiky hairs around the reproducing parts, which are used to attach to females during mating. Sizes can reach up to 2.5-3mm, with females being only slightly larger than males.
Breeding and dietary information
Vinegar flies can be found all around the world, albeit with a greater variety of species in tropical regions. As a result, habitats vary, including deserts, rainforests, swamps, alpine zones, as well as cities. Some northern species hibernate, while, in others, adults die in the wintertime.
Both males and females of the D. Melanogaster species are polygamous, having multiple sexual partners at the same time. Copulation lasts around 15-20 minutes. Females then lay around 5 eggs at a time, 400 in total, in what they consider to be suitable material: rotting fruit, decaying mushrooms, etc. The eggs are around 0.5 mm in length and, under ideal conditions, hatch in 12-15 hours. The larval stage lasts around 4 days, moulting thrice, at 24, 48 and then 96 hours following hatching. Pupation comes next, and then a 4-day metamorphosis to adulthood. Females become able to reproduce only 8-12 hours into adulthood.
A D. melanogaster’s development and lifespan are highly dependent on temperature. At 29°C, an individual develops, from egg to adult, in about 7 days. This is the shortest known development time, with the needed time period then increasing both at lower and at higher temperatures, in the latter case due to heat stress. Ideal conditions (25°C) have individuals developing over 8,5 days. A temperature of 18°C has the development time increasing to 19 days, while one of 12°C, to 50 days or more. Development time is also affected by factors such as crowded conditions, in which case the emerging individuals are also smaller. Generally, a total lifespan lasts around 30 days at 29 degrees Celsius.
When it comes to the predators of the Drosophila species, these include: larvae of larger flies, robber flies, staphylinid beetles, ants, etc.
Vinegar flies are attracted to any and all foods that are rotting or fermenting, the most common of which are apples, bananas, tomatoes, potatoes, onions, etc. The liquid that remains at the bottom of beer bottles or cans, as well as the wet remains of food that gather in drains can also be enough organic material to support a population of vinegar flies. Larvae feed on microorganisms that decompose fruits, such as the yeast, as well as the sugar of fruits themselves.
Vinegar flies as pests
All species of flies are well-known due to the tendency they have to effortlessly find ways to enter homes in search of warmth and food. Not only is the constant buzzing they bring along annoying, but their presence is also potentially unsanitary, both due to the bacteria they may carry on their legs and easily transfer onto food or surfaces that food comes in contact with, as well as due to the fact that, if they are unsuccessful in finding a way back outside, they die, leaving behind corpses in all sorts of places.
Vinegar flies, in particular, are an even bigger nuisance, seeing as they are attracted to foods that are rotting or fermenting, creating an even more unpleasant situation and increasing the risk that they may transfer dangerous bacteria onto surfaces that are supposed to be sterile. The most common time of the year that people report encountering problems with vinegar flies is the end of summer, when ripe fruits and vegetables are abundant. Once the cold comes, most flies die, but if you live in a warm climate, they can become an annoyance that is very difficult to stand.
On the other hand, D. melanogaster (the common fruit fly), has been used extensively as a model organism in developmental biology, in research on genetics, physiology, microbial pathogenesis, and life history evolution. This is because it is an animal species that is very easy to take care of, breeding quickly and laying many eggs. The importance of its contribution to human health was recognized by the Nobel prize in medicine of 1995.
Unlike other larger pests, it is more difficult to fight the flies by exclusion. However, there are preventive measures which can help in keeping these flies at bay. Having a constant level of sanitation in your home, you will be able to stop vinegar flies from developing in a large number. Pruning, trapping, baiting and spraying with insecticides are all methods that need to be applied when fighting these pests. However, the best preventive measure, as with most other pests, is sanitation. You can find more details in our article regarding ways in which you can ‘Prevent infestation with Vinegar Flies’.
After removing attractants, you can apply several other methods of control, be they natural or chemical, in order to get rid of an infestation with vinegar flies. No matter what method you choose, you can see details about them in our article about ‘How to get rid of Vinegar Flies’.
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