Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly" or "pomace fly".[a][4] Starting with Charles W. Woodworth's 1901 proposal of the use of this species as a model organism,[5][6] D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. As of 2017, five Nobel Prizes have been awarded to drosophilists for their work using the insect.[7][8]

Melanogaster is typically used in research owing to its rapid life cycle, relatively simple genetics with only four pairs of chromosomes, and large number of offspring per generation.[9] It was originally an African species, with all non-African lineages having a common origin.[10] Its geographic range includes all continents, including islands.[11] D. melanogaster is a common pest in homes, restaurants, and other places where food is served.[12]

Flies belonging to the family Tephritidae are also called "fruit flies". This can cause confusion, especially in the Mediterranean, Australia, and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest.

Flies are yellow-brown, with brick-red eyes and transverse black rings across the abdomen. The brick-red color of the eyes of the wild type fly are due to two pigments:[13] xanthommatin, which is brown and is derived from tryptophan, and drosopterins, which are red and are derived from guanosine triphosphate.[13] They exhibit sexual dimorphism; females are about 2.5 mm (0.10 in) long; males are slightly smaller with darker backs. Males are easily distinguished from females based on colour differences, with a distinct black patch at the abdomen, less noticeable in recently emerged flies, and the sexcombs (a row of dark bristles on the tarsus of the first leg). Furthermore, males have a cluster of spiky hairs (claspers) surrounding the reproducing parts used to attach to the female during mating. Extensive images are found at FlyBase.[14] Drosophila melanogaster flies can sense air currents with the hairs on their backs. Their eyes are sensitive to slight differences in light intensity and will instinctively fly away when a shadow or other movement is detected.[15]

Under optimal growth conditions at 25 °C (77 °F), the D. melanogaster lifespan is about 50 days from egg to death.[16] The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. The shortest development time (egg to adult), 7 days, is achieved at 28 °C (82 °F).[17][18] Development times increase at higher temperatures (11 days at 30 °C or 86 °F) due to heat stress. Under ideal conditions, the development time at 25 °C (77 °F) is 8.5 days,[17][18][19] at 18 °C (64 °F) it takes 19 days[17][18] and at 12 °C (54 °F) it takes over 50 days.[17][18] Under crowded conditions, development time increases,[20] while the emerging flies are smaller.[20][21] Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. Drosophila melanogaster is a holometabolous insect, so it undergoes a full metamorphosis. Their life cycle is broken down into 4 stages: embryo, larva, pupa, adult.[22] The eggs, which are about 0.5 mm long, hatch after 12–15 hours (at 25 °C or 77 °F).[17][18] The resulting larvae grow for about 4 days (at 25 °C) while molting twice (into second- and third-instar larvae), at about 24 and 48 h after hatching.[17][18] During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself. The mother puts feces on the egg sacs to establish the same microbial composition in the larvae's guts that has worked positively for herself.[23] Then the larvae encapsulate in the puparium and undergo a 4-day-long metamorphosis (at 25 °C), after which the adults eclose (emerge).[17][18]

Males perform a sequence of five behavioral patterns to court females. First, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Soon after, the male positions himself at the rear of the female's abdomen in a low posture to tap and lick the female genitalia. Finally, the male curls his abdomen and attempts copulation. Females can reject males by moving away, kicking, and extruding their ovipositor.[24] Copulation lasts around 15–20 minutes,[25] during which males transfer a few hundred, very long (1.76 mm) sperm cells in seminal fluid to the female.[26] Females store the sperm in a tubular receptacle and in two mushroom-shaped spermathecae; sperm from multiple matings compete for fertilization. A last male precedence is believed to exist; the last male to mate with a female sires about 80% of her offspring. This precedence was found to occur through both displacement and incapacitation.[27] The displacement is attributed to sperm handling by the female fly as multiple matings are conducted and is most significant during the first 1–2 days after copulation. Displacement from the seminal receptacle is more significant than displacement from the spermathecae.[27] Incapacitation of first male sperm by second male sperm becomes significant 2–7 days after copulation. The seminal fluid of the second male is believed to be responsible for this incapacitation mechanism (without removal of first male sperm) which takes effect before fertilization occurs.[27] The delay in effectiveness of the incapacitation mechanism is believed to be a protective mechanism that prevents a male fly from incapacitating his own sperm should he mate with the same female fly repetitively. Sensory neurons in the uterus of female D. melanogaster respond to a male protein, sex peptide, which is found in semen.[28] This protein makes the female reluctant to copulate for about 10 days after insemination. The signal pathway leading to this change in behavior has been determined. The signal is sent to a brain region that is a homolog of the hypothalamus and the hypothalamus then controls sexual behavior and desire.[28] Gonadotropic hormones in Drosophila maintain homeostasis and govern reproductive output via a cyclic interrelationship, not unlike the mammalian estrous cycle.[29] Sex peptide perturbs this homeostasis and dramatically shifts the endocrine state of the female by inciting juvenile hormone synthesis in the corpus allatum.[30]

D. melanogaster is often used for life extension studies, such as to identify genes purported to increase lifespan when mutated.[31] D. melanogaster is also used in studies of aging. Werner syndrome is a condition in humans characterized by accelerated aging. It is caused by mutations in the gene WRN that encodes a protein with essential roles in repair of DNA damage. Mutations in the D. melanogaster homolog of WRN also cause increased physiologic signs of aging, such as shorter lifespan, higher tumor incidence, muscle degeneration, reduced climbing ability, altered behavior and reduced locomotor activity.[

Under optimal growth conditions at 25 °C (77 °F), the D. melanogaster lifespan is about 50 days from egg to death.[16] The developmental period for D. melanogaster varies with temperature, as with many ectothermic species. The shortest development time (egg to adult), 7 days, is achieved at 28 °C (82 °F).[17][18] Development times increase at higher temperatures (11 days at 30 °C or 86 °F) due to heat stress. Under ideal conditions, the development time at 25 °C (77 °F) is 8.5 days,[17][18][19] at 18 °C (64 °F) it takes 19 days[17][18] and at 12 °C (54 °F) it takes over 50 days.[17][18] Under crowded conditions, development time increases,[20] while the emerging flies are smaller.[20][21] Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. Drosophila melanogaster is a holometabolous insect, so it undergoes a full metamorphosis. Their life cycle is broken down into 4 stages: embryo, larva, pupa, adult.[22] The eggs, which are about 0.5 mm long, hatch after 12–15 hours (at 25 °C or 77 °F).[17][18] The resulting larvae grow for about 4 days (at 25 °C) while molting twice (into second- and third-instar larvae), at about 24 and 48 h after hatching.[17][18] During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit itself. The mother puts feces on the egg sacs to establish the same microbial composition in the larvae's guts that has worked positively for herself.[23] Then the larvae encapsulate in the puparium and undergo a 4-day-long metamorphosis (at 25 °C), after which the adults eclose (emerge).[17][18]

Females become receptive to courting males about 8–12 hours after emergence.[33] Specific neuron groups in females have been found to affect copulation behavior and mate choice. One such group in the abdominal nerve cord allows the female fly to pause her body movements to copulate.[28] Activation of these neurons induces the female to cease movement and orient herself towards the male to allow for mounting. If the group is inactivated, the female remains in motion and does not copulate. Various chemical signals such as male pheromones often are able to activate the group.[28]

Also, females exhibit mate choice copying. When ****** females are shown other females copulating with a certain type of male, they tend to copulate more with this type of male afterwards than naive females (which have not observed the copulation of others). This behavior is sensitive to environmental conditions, and females copulate less in bad weather conditions.[34]

. melanogaster males exhibit a strong reproductive learning curve. That is, with sexual experience, these flies tend to modify their future mating behavior in multiple ways. These changes include increased selectivity for courting only intraspecifically, as well as decreased courtship times.

Sexually naïve D. melanogaster males are known to spend significant time courting interspecifically, such as with D. simulans flies. Naïve D. melanogaster will also attempt to court females that are not yet sexually mature, and other males. D. melanogaster males show little to no preference for D. melanogaster females over females of other species or even other male flies. However, after D. simulans or other flies incapable of copulation have rejected the males' advances, D. melanogaster males are much less likely to spend time courting nonspecifically in the future. This apparent learned behavior modification seems to be evolutionarily significant, as it allows the males to avoid investing energy into futile sexual encounters.[35]

In addition, males with previous sexual experience modify their courtship dance when attempting to mate with new females—the experienced males spend less time courting, so have lower mating latencies, meaning that they are able to reproduce more quickly. This decreased mating latency leads to a greater mating efficiency for experienced males over naïve males.[36] This modification also appears to have obvious evolutionary advantages, as increased mating efficiency is extremely important in the eyes of natural

. melanogaster males exhibit a strong reproductive learning curve. That is, with sexual experience, these flies tend to modify their future mating behavior in multiple ways. These changes include increased selectivity for courting only intraspecifically, as well as decreased courtship times.

Sexually naïve D. melanogaster males are known to spend significant time courting interspecifically, such as with D. simulans flies. Naïve D. melanogaster will also attempt to court females that are not yet sexually mature, and other males. D. melanogaster males show little to no preference for D. melanogaster females over females of other species or even other male flies. However, after D. simulans or other flies incapable of copulation have rejected the males' advances, D. melanogaster males are much less likely to spend time courting nonspecifically in the future. This apparent learned behavior modification seems to be evolutionarily significant, as it allows the males to avoid investing energy into futile sexual encounters.[35]

In addition, males with previous sexual experience modify their courtship dance when attempting to mate with new females—the experienced males spend less time courting, so have lower mating latencies, meaning that they are able to reproduce more quickly. This decreased mating latency leads to a greater mating efficiency for experienced males over naïve males.[36] This modification also appears to have obvious evolutionary advantages, as increased mating efficiency is extremely important in the eyes of natural