Two signalling pathways work together to reshape olfactory responses so that hungry flies are attracted to food sources they would otherwise ignore.
Related research article Ko KI, Root CM, Lindsay SA, Zaninovich OA, Shepherd AK, Wasserman SA, Kim SM, Wang JW. 2015. Starvation promotes concerted modulation of appetitive olfactory behavior via parallel neuromodulatory circuits. eLife 4:e08298. doi: 10.7554/eLife.08298
A common expression would have us believe that ‘you can catch more flies with honey than with vinegar’. But this is not true in the case of the fruit fly Drosophila melanogaster (xkcd, 2007). Adult flies forage for microbes on overripe fruit, relying on their sense of smell to detect the acetic acid (the chemical that gives vinegar its pungent aroma) that accumulates as the fruit ferments. However, flies tend to ignore or even avoid both low levels of vinegar (which suggest that the fruit is not ripe enough) and high levels of vinegar (which suggest that the fruit might be rotten).
Now, in eLife, Jing Wang and co-workers at the University of California, San Diego—including Kang Ko as first author—elegantly reveal what happens in flies brains that allows them to pursue a broader range of vinegar odor concentrations when hungry (Ko et al., 2015). Their data also show that starvation has a more nuanced influence on the early processing of olfactory information than was previously anticipated: hunger does more than just tune up the flies sensitivity to food odors. Instead, it triggers specific responses (both excitatory and inhibitory) that encourage the flies to forage on sub-optimal food sources. In doing so, Ko et al. possibly provide additional evidence to support the notion that it is not wise to go grocery shopping on an empty stomach, lest hunger signals may impair your ability to discriminate good food from bad.
Ko et al.s work is the culmination of a series of studies that have addressed how Drosophila process information about this important food odor. In fruit flies, much like in humans and other vertebrates, the olfactory neurons that detect specific volatile chemicals wire up to discrete clusters of synapses within the brain called glomeruli. Olfactory neurons that detect the same chemical all connect to the same glomerulus. Depending on the concentration, vinegar odor activates 6 to 8 of the 40 or so glomeruli in the fruit fly brain. However, a previous landmark study from the Wang group revealed that the activity of a single olfactory glomerulus, referred to as DM1, could explain most of a flys attraction to vinegar (Semmelhack and Wang, 2009). Turning off the receptors that connect to DM1 caused the flies to ignore the odor of vinegar. On the other hand, restoring only the activity of DM1 neurons in otherwise ‘anosmic’ flies (that is, flies that have lost almost all sense of smell) was enough to make them attracted to vinegar again.
Higher concentrations of vinegar recruit just one extra glomerulus, called DM5, and the activity of DM5 on its own can explain why flies avoid vinegar if the odor is too strong (Semmelhack and Wang, 2009). Hence, the competitive interaction between DM1 and DM5 (which are activated at different vinegar odor concentrations) may ultimately determine whether the fly decides to approach a potential food source or to stay away.
Hunger has a profound impact on animal behavior, and hungry flies find a small drop of vinegar-laced food much more quickly than flies that have been fed (Root et al., 2011). The hormone insulin indirectly mediates this effect. Starvation causes insulin levels to plummet, triggering a chain of events that ultimately causes DM1 olfactory neurons to increase the expression of a specific receptor protein. This receptor detects a signaling molecule called ‘short neuropeptide F’. Upon binding to the receptor, this neuropeptide effectively amplifies, or turns up the ‘gain’ of, DM1 activity. Since DM1 neurons control a fruit flys attraction to vinegar, this finding seemed to elegantly explain how insulin signaling can lead hungry flies to look more widely for food.
It now transpires that this is not the whole story. By extending the range of odor concentrations tested, Ko et al. now find that this mechanism only explains how hungry flies boost their attraction to low vinegar odor concentrations. At higher concentrations, starved flies still pursue vinegary food more robustly than fed controls, even when signaling mediated by short neuropeptide F is reduced (Ko et al., 2015). Could an additional neuropeptide account for this difference? To search for this missing hunger signal, Ko et al. surveyed other receptor proteins, looking for those that were increased in sensory neurons as a result of starvation. The Tachykinin receptor (called DTKR for short) emerged as a strong candidate, especially because it was known that it can tune down the responses of the flys olfactory neurons (Ignell et al., 2009).
The rest of Ko et al.s story beautifully follows a logical script: knocking down the levels of DTKR indeed reduced food-finding behavior in hungry flies exposed to high, but not low, vinegar odor concentrations. Similarly, DM5 (the glomerulus responsible for avoidance of high levels of vinegar) was less active in starved flies, but its activity could be brought back up to that of a fed fly when DTKR was knocked-down. Finally, Ko et al. identified insulin as the likely signal that acts upstream of DTKR in starving flies.
Taken together, the data suggest a model in which falling insulin levels in starving flies trigger two complementary neuropeptide signaling systems involving short neuropeptide F and Tachykinin. One helps the transmission of signals at the DM1 glomerulus, which makes the flies more sensitive to attractive food odors. In parallel, the other turns down transmission at DM5, which makes the flies less likely to avoid normally unpleasant or aversive smells. Together, these systems allow flies to pursue less-than-optimal food sources in times of shortage ( ).
This study powerfully demonstrates the strengths of the fly model as a platform to study how the brain computes sensory stimuli. From clever behavioral assays, to sophisticated genetic manipulations and imaging of brain activity, the work describes how an important sensory cue is handled in different ways depending on the internal state of the animal (that is, hungry or not). Since what is true for the fly is often—at least in outline—true for man, the area of research is now ripe to contribute principles of sensory processing that may be applicable to many, if not all, animal species.
Liquid dish soap is exactly what you need to drown the flies. Sugar and vinegar attract them, while the soap breaks the surface tension of the liquid to trap the flies instead of keeping them sitting on the surface.
The end of summer always brings with it hoards of fruit flies. I learned this trick from my friend Angella and every year I bust it out like some kind of twisted party trick. Pouring out tiny fruit fly bodies every morning when I empty the trap is so satisfying, you guys. So satisfying.
Mix together: 2 Tbsp white vinegar, 2 Tbsp granulated sugar, and 2 cups warm water. I like to make my fruit fly trap in a pie plate so there is lots of surface area to catch the most fruit flies. After the sugar has dissolved, add a few drops of liquid dish soap. The vinegar and sugar attract the fruit flies, the soap changes the surface tension of the water so the flies cant escape, and the water drowns the little suckers. I show no mercy.
The rest of Ko et al.s story beautifully follows a logical script: knocking down the levels of DTKR indeed reduced food-finding behavior in hungry flies exposed to high, but not low, vinegar odor concentrations. Similarly, DM5 (the glomerulus responsible for avoidance of high levels of vinegar) was less active in starved flies, but its activity could be brought back up to that of a fed fly when DTKR was knocked-down. Finally, Ko et al. identified insulin as the likely signal that acts upstream of DTKR in starving flies.
Two signalling pathways work together to reshape olfactory responses so that hungry flies are attracted to food sources they would otherwise ignore.
Related research article Ko KI, Root CM, Lindsay SA, Zaninovich OA, Shepherd AK, Wasserman SA, Kim SM, Wang JW. 2015. Starvation promotes concerted modulation of appetitive olfactory behavior via parallel neuromodulatory circuits. eLife 4:e08298. doi: 10.7554/eLife.08298
It now transpires that this is not the whole story. By extending the range of odor concentrations tested, Ko et al. now find that this mechanism only explains how hungry flies boost their attraction to low vinegar odor concentrations. At higher concentrations, starved flies still pursue vinegary food more robustly than fed controls, even when signaling mediated by short neuropeptide F is reduced (Ko et al., 2015). Could an additional neuropeptide account for this difference? To search for this missing hunger signal, Ko et al. surveyed other receptor proteins, looking for those that were increased in sensory neurons as a result of starvation. The Tachykinin receptor (called DTKR for short) emerged as a strong candidate, especially because it was known that it can tune down the responses of the flys olfactory neurons (Ignell et al., 2009).
Taken together, the data suggest a model in which falling insulin levels in starving flies trigger two complementary neuropeptide signaling systems involving short neuropeptide F and Tachykinin. One helps the transmission of signals at the DM1 glomerulus, which makes the flies more sensitive to attractive food odors. In parallel, the other turns down transmission at DM5, which makes the flies less likely to avoid normally unpleasant or aversive smells. Together, these systems allow flies to pursue less-than-optimal food sources in times of shortage ( ).
DIY FLY Trap to Get Rid of Flies and Fruit Fly
FAQ
Does sugar and vinegar kill flies?
Can vinegar attract flies?
Are flies attracted to sugar?
Does vinegar attract flies?
The trap mentioned utilizes a mixture that includes sugar, likely because flies are more likely to be enticed by its sweetness. Although vinegar can also attract flies, the lure of sugar proves to be more effective in capturing these pesky insects. So, when it comes to catching flies, it appears that sugar has the upper hand over vinegar.
Do flies eat sugar & vinegar?
Like rotten produce, mixing sugar and vinegar will entice flies. You can either make a trap or use a premade one and add the sugar and vinegar. Ensure you securely cover the container to ensure flies can’t escape. Adding a rubber band around plastic wrap provides additional security.
Does malt vinegar kill flies?
While malt vinegar isn’t for regular cleaning, it does a superb job at ridding your house of flies. Like rotten produce, mixing sugar and vinegar will entice flies. You can either make a trap or use a premade one and add the sugar and vinegar. Ensure you securely cover the container to ensure flies can’t escape.
Can you catch more flies with honey or vinegar?
Image Hunger changes how the fly olfactory system processes food odors A common expression would have us believe that ‘ you can catch more flies with honey than with vinegar ’. But this is not true in the case of the fruit fly Drosophila melanogaster ( xkcd, 2007 ).