Presented by Terry Lynch (TAL)
Artist, Poet, Philosopher and Naturalist
Part I: Application of Torque to Induce Simultaneous Flight Response and Synchrony in Drosophila sp.
A most interesting area for study of alate Drosophila is their simultaneous flight response and synchrony which occurs with the application of torque or change in motion; ie, acceleration. This behavior was first observed by me on Christmas eve of 1996 while raring wild, alate Drosophila in large quantities in mason jars upon a media of yeast and apple sauce.
I had begun to rear and study wild Drosophila in September of 1996 with the objective of observing all aspects of their behavior, specifically their courtship. This was by no means my first study of Drosophila or flies in general. I had reared vestigial varieties of fruit flies in 1970-71 and learned much about the basic handling and usage of Drosophila in genetics. I had also studied and reared both house flies and bottle flies, using raring techniques I had learned at IFAS in Gainesville, Florida. I once kept a line of bottle flies in my bedroom for over a year, observing every aspect of its life history. I don't recommend this for anyone too interested in girl friends, but it may be a good way to get a divorce!
In mid-September of 1996 I had occasion to collect some wild Drosophila after a dinner in which wine was served. The fruit flies came to feast upon droplets of wine remaining in a glass left sitting out over night. I believe it was, "Soave, the leading and most popular dry white wine of Italy," since I and my fruit flies only drink the best. Thus from a few wild Drosophila I soon had thousands!
Initially my objective was to determine what stimuli would cause flight. I suspected that fruit flies would perceive movement, as when one swats at a fly and it quickly flies away; however, I found that moving one's hand or an object in close proximity to a jar of fruit flies did not induce flight. Nor did a loud clap of one's hands or a vibration, such as hitting the table near a jar of fruit flies. Then I noticed that when a jar of resting fruit flies is disturbed simply by rotating their jar, the mass of fruit flies jump and fly in simultaneous, synchronous response! In fact if you listen with a sharp ear you can hear the buzz of the fruit flies as they take flight much like a flock of birds rising in simultaneous response to a gun shot.
To demonstrate this behavior secure a quart or gallon size mason jar containing a stock culture (1000 or more adult alate fruit flies) upon a large circular base (a plate, pizza pie pan or turn table will work fine), such that the jar of fruit flies sets in the center of the base and may be rotated about an axis perpendicular to the center of the plane of the base. A piece of double sided tape set under the jar will usually do the job of holding the jar securely in place upon the base.
Leave the jar undisturbed in a quite dimly lighted (or equally lighted) room for an hour or so. Then holding onto the edge of the circular base give it a quick turn or twist to rotate 30-45 degrees about an axis through the center of the jar and the base. This will produce an acceleration or change in torque. Note that this quick start-stop motion induces the fruit flies to simultaneous jump and fly as if in synchrony. Their halters detect a change in motion or acceleration and the fruit flies all at once jump and fly as if they were falling and took wing.
This is the same type of induced response one observes when firing a gun and a flock of birds all take flight together; when flashing a light and a meadow of fireflies all blink simultaneously in response or when a group of chirping birds or insects are suddenly startled and all fall silent. The question is, to what degree is this simultaneous flight response in Drosophila also a synchronous behavior? I conjecture that it is both a simultaneous response and a synchronous response because the group of Drosophila so induced to fly all are beating their wings in obvious synchrony to some high degree! In fact this induced simultaneous flight response represents the most basic form of synchronous group behavior.
To my knowledge no one else has ever noted this particular simultaneous or basic synchronous stimulus-response reaction in Drosophila. I also suspect it is a common behavior in may types of flies; I would say all flies, but that may be saying a bit much. However, it would be interesting to observe how common this simultaneous flight response is in flies and this represents an area of study students might want to make.
I postulate this simultaneous flight response indeed results in synchronous wing beat of alate Drosophila and that it is the same type of basic behavior which results in fireflies blinking in synchrony or crickets, katydids or other insects chirping their wings in synchrony. It is also the same basic stimulus-response that causes a swarm of grasshoppers to take flight together or a flock of birds to rise and fly in apparent unison. Each individual in the swarm or flock is simply responding simultaneously to the same stimulus; their reaction time being identical so as to result in synchronous behavior. In fact in a large flock of birds spread over a great distance, a sound may alert the flock which appear to take flight in a wave as the sound travels over the flock, the near birds rising first and the further birds rising quickly there after as the sound reaches them (I am sure that many a naturalist, bird watcher or hunter has observed this behavior which has even been filmed).
That alate Drosophila exhibit this basic simultaneous flight response to a change in torque means that there exist a species that is easy to rear and can be used to investigate this behavior. Some factors to determine are the exact interval of time involved in causing the flight response, the amount of torque (force) or change of motion (acceleration) required to produce a response and how temperature effects the response. It would also be interesting to measure the degree of synchrony which occurs in the wing beat or wing vibrations of a mass of fruit flies all induced to fly simultaneously, and the degree, if any, in synchronous wing beat that occurs; how it is lost, adopted or maintained by the group?
I suspect recording of wing beats would demonstrate a high degree of synchrony given the mass of fruit flies all take to the air simultaneously and hence this would establish that the basic stimulus-response behavior also results in the mass of fruit flies beating their wings in synchrony for some amount of time; that the buzz produced by this mass of fruit flies is not that of many individuals beating their wings independently, but that the mass tend to act as a swarm and all jump, fly and beat their wings in synchrony to some high and measurable degree.
I have, in fact, performed this experiment with mason jars containing thousands of fruit flies and it is possible to hear the buzz or hum of the fruit flies as they jump and fly in apparent synchrony! Of course my unaided ears are not so good that I'd wager every fruit fly is beating its wings in synchrony, but I bet a good percentage of them are. Since I don't have the electronic equipment necessary to make this determination, I'll leave that task to someone who is more rich than I. I'm pretty sure if you amplify the sound 100-1000 times and run the output through an oscilloscope you will see not noise, but that the fruit flies induced to fly by a change in torque are beating their wings in synchrony to a high degree.
I postulate that the induced simultaneous flight response in fruit flies is a basic stimulus-response behavior; that it is, in fact, the most basic or root form of synchronous behavior. In fact the synchronous flashing of fireflies is nothing more than simple "see-me-blink-now-on-the-count-of-one-two-three-you-blink" stimulus-response reaction complicated by the fact that a multitude of individuals all exhibit the same response to the same stimulus which is transferred and extended over a distance beyond the perception of a single individual through the linking of many individuals in close proximity. This becomes apparent when one sees a similar stimulus-response in Drosophila to a change in torque or change in motion (acceleration). In the case of Drosophila the mass of fruit flies all jump and fly at the same instance which means their wings are beating in synchrony to a greater degree than before the stimulus (change in torque) which resulted in a mass flight response.
It may seem a large jump to make comparing behavior in Drosophila to that of fireflies. But perhaps the jump is not so far when we realize both fireflies and Drosophila communicate in the mating process. Fruit flies use wing vibrations and a courtship dance; fireflies use flashing light and are often flying in their courtship. Hence it is not too far a leap to associate a simultaneous stimulus-response in fruit flies induced to fly and beat their wings in synchrony to that of synchronous blink response in fireflies, all made to flash in simultaneous response to the stimulus of a bright flashing light. In both cases a stimulus results in a simultaneous response of a group; in the case of fireflies they are perhaps better adapted than are fruit flies at keeping in time or synchrony with one another.
Is the simultaneous stimulus-response of Drosophila to change in torque a true synchronous behavior? Perhaps it is or is not, but in the very least it is a basic type of group behavior similar to that of: (a) a meadow of fireflies all blinking in simultaneous response to a flash of light; (b) crickets all simultaneously stopping their chirp when they hear a noise; or, (c) a flock of birds all taking flight in the same instant that they hear a gun fire.
Obviously to have true synchrony you must have a behavior which repeats itself over time with some high degree of regularity and involves a group of individuals all chirping, singing, flashing or beating their wings in synchrony. This requires that the insect producing the stimulus must also be able to receive the stimulus such that it may respond in kind or in synchrony to that degree that the species is able to maintain a tune, rhythm or pattern of behavior.
I would suggest that the simultaneous response to applied torque observed in Drosophila is a synchronous group response in its most basic form, and that this type of response does play a role in synchronous behavior. In the case of some insects, when the time to respond to a stimulus (as to a flash of light in the case of some species fireflies) equals the time between stimuli (or flashes), then a group can easily establish a synchronous behavior (provided the insect under consideration has the necessary sensory receptors and the organs to produce sound, light or other stimulus). This is true because any individual stimulated by the group behavior will be in synchrony with the group when they join by responding to the behavior. In fact, if a high percentage of fruit flies all jump and fly simultaneously, it is highly probable their wings will be beating in synchrony, since they started vibrating in the same instant and each individual has an identical wing beating frequency range. So what begins as simultaneous flight response to applied torque results is a genuine synchronous behavior!
The remaining challenge for investigators is to study and measure this response in Drosophila to gleam what knowledge can be had and apply this knowledge to the understanding of synchronous behavior.
Part II: Stimulus-Response and Synchronous Behavior in Drosophila: Theoretical Considerations
When is an induced stimulated response also a synchronous behavior? Obviously the answer is when a group of individuals also exhibit a repeated behavior such as wing beat or flashing in synchrony over a duration of time. Since a group of Drosophila consist of identical individuals which all beat their wings at the same frequency range, if a high percentage of Drosophila in a group is induced to jump and fly at the same instant, the result will be a synchronous beating of wings; ie, all Drosophila which start their wing beats vibrating at the same instant will be in synchrony at least for the same duration of time as they remain in flight.
An area for further study is to determine: (a) what percentage of Drosophila of a group can be induced to jump and fly with the application of torque; (b) what percentage of a group induced to fly will beat their wings in synchrony; (c) how long will synchrony be maintained in the group; (d) whether or not other Drosophila in the group shift, set or train their wings to beat in synchrony with the group of jumping, flying Drosophila; (e) whether or not over time a group of individuals can be taught to beat their wings in synchrony by repeating the change in torque experiment frequently, say every 5-10 minutes?
This later experiment might reveal that learning plays a role in synchronous behavior for insects and would be an observation of some significance for its implications with respect to synchronous behavior in other insects such as fireflies. That is to say, individuals of a group over time may learn to flash in synchrony simply because they are responding over and over by flashing after as set duration to the flash of the group.
This brings up the problem of which came first, the chicken or the egg; ie, the flash or the response to the flash? It also make one wonder how is this behavior (or any behavior) encoded genetically? Then one wonders how this behavior originally evolved so as to be genetically encoded? This probably involved a very slow change in genes coupled with an equally slow change in courtship behavior, that over time new species with characteristic and unique courtship behavior have occurred. The study of courtship in Drosophila may enable one to gain some knowledge of how behavior and genes are linked. Genetic engineering of Drosophila may enable one to gleam even a greater insight into how genes encode courtship behavior.
Part III: Experimental Considerations for Future Study with Respect to Simultaneous Flight Response as Induced by Application of Torque in Drosophila
What is the ratio of noise to synchronous wing beat in a mass of alate Drosophila induced to fly by the introduction of torque? Given a group of 1,000 or more fruit flies, what percentage beat their wings in synchrony? How does the number of fruit flies beating their wings in synchrony vary when a jump and flight response is initiated using application of torque?
Does synchronous wing beat of Drosophila increase in the mass when torque is applied and removed? This is an analogous behavior to flashing a bright light across a meadow or mangrove of active fireflies and causing many fireflies to flash in response to the signaling light. To what degree can a mass of Drosophila induced to fly and beat their wings in synchrony maintain a high degree of synchrony over time?
Can a mass of fruit flies learn to maintain synchronous wing beat by repeating the application of torque with high frequency, say every 5-10 minutes? If so can a mass of fruit flies "A" beating their wings in synchrony induce another mass of fruit flies "B" not trained to beat their wings in synchrony to also shift, set or train their wings to beat in synchrony with group "A"?
If this later behavior can be established it would perhaps give some insight into what role, if any, training has in synchronous behavior observed in nature; ie, do individual fireflies have the ability to learn to flash in synchrony with a group? This is not so far fetched an idea, as it may be exactly what is happening in the case where Photinus pyralis males flash promptly in response to other males, as if trying to synchronize or learn to flash with the group that is already flying and flashing to some degree in synchrony with other members in close proximity. I suggest that this basic behavior of joining a group is a basic form of stimulus-response that is akin to learning in its most rudimentary form.
These observations, theoretical considerations and ideas for experimental investigation are published that others may take some interest in this area of insect behavior. I do not make any claims to know everything or to even be an authority on insect behavior. Nor do I set into stone any ideas, beliefs or opinions with this present study. But I do hope it sparks interest and that others may find herein something of value from which to begin their own inquiries.
I would appreciate hearing from any amateur naturalist or even professional entomologist who read this report and have something of value to add to the study of insect behavior. Please feel free to correspond by writing to Terry Lynch
Project K9 | Blinks and Links | Bioluminescence in Fireflies: The luciferase-luciferin reaction in Photinus pyralis | Part I: Application of Torque to Induce Simultaneous Flight Response and Synchrony in Drosophila | The Amateur Naturalist | Firefly Notebooks | Feeding behavior of Photinid larvae | Flash Keys in Fireflies | Contact the author