Two years back, I made an interesting yet strange observation about the movement of a housefly. I have documented its movements in detail (Housefly Movements). That time I tried to ask many people about such strange pattern of movement but I didn’t get any answers.
Has any one observed that particular behavior before?
Few days back, I recieved some amazing and apparently well researched answers from a girl – Tamanna. I am positive thats its worth sharing with you all. Kindly have a look at the answers:
1. First u said that FLUIE(thats the name fr the fly lets say), was following a specific hexagonal path continuously. Sometimes, for few seconds, it changed its speed or got a bit higher or got drifted from its hexagonal path but then quickly came back to same path and started following same hexagonal pattern on horizontal plane.
Ans: Actually there are different kinds of houseflies too…Hwever, mostly just two of them inhabit human homes and habitats. One is the Common Housefly, Musca domestica.
The second is the Lesser Housefly, Fannia canicularis. Major ways to differentiate between the two forms is that the lesser housefly is small and slender in comparison to M.
domestica and also the media vein (4th longitudinal vein) in the wings of M.domestica has a sharp upward bend. but that of F. canicularis is straight. Also it has been observed that the males of Lesser houseflies fly in a very distinctive way….They choose a spot in a room often beneath a hanging lamp or something of the sorts and fly as if they were following the sides of a triangle or quadrilateral, hovering and turning sharply at the corners. And a single fly will continue to follow the same course for long periods! (The International Wildlife Encyclopedia, by Maurice Burton, Robert Burton; Pg- 1241). So well if this is true than our FLUIE was probably a male Fannia canicularis!
2. At the hexagonal edge, it took such a sudden sharp turn as if it had banged on to some unseen wall. It is to be noticed that the speed of fly was almost uniform throughout the process. Even after 20 minutes, it was still following the same pattern. So, I tried to experiment with it. I blew the air hard towards it with my mouth. It suddenly jumped into air but to my utter astonishment, it quickly returned to same height and same plane and started following same pattern. I went near to that hexagonal circuit, which it was following. The fly seemed to be unfazed by my presence. Then I tried to get into the middle of hexagonal path, the fly dived aside and started following same pattern few centimeters away from me. When I moved out of that virtual hexagon, back to my chair (about a meter away), surprisingly, the fly came back to its original hexagonal path.
Ans: Fly has two compound eyes…wich have like 1600 or so facets allowing for a wide angle of observation of its surrounding..approx 360 degrees I am nt very sure about the angle. Anyhw, so the main thing is that in insects, during flight, the image across the retina is a combination of inputs from stationary backgrounds that are initiated by self movement and from other moving objects in the field of view. Both these generate complex input patterns that alter rapidly in configuration, and have very high angular velocities as the fly is moving around. This is possible due to the fly’s visual system wich can record very rapid changes in the surroundings. This visual system in a fly is made up of two motion dependent visual systems:
1. The Large Field system– it is most sensitive to the motion of large patterns and controls the fly’s torque mainly at low oscillation frequencies (below 0.1Hz)..i.e. leads to turning response of low frequencies in the insect. this large field system is sorta like it makes the fly cope with the consequences of its visual impact due to active self-motion. its like the retina of the fly’s eye obtains high frequency samples of more or less stationary images. this leads to blurring of the image. blurring of an image wich is flashed aross the retina depends upon two things…
a) response speed of the eye.
b) its spatial resolution capacity.
for eg take a human eye..it has high spatial resolution for the object it is viewing but the response speed is low..i.e. it takes time to resolve the image. but in insects, the spatial
resolution = low however, the response speed = high…i.e. it can tolerate movements at higher speeds without losing resolution.
2. The Small Field System–this system lends to the detection of relatively small moving patterns and leads to turning response of high frequency in the insect.
So its simply said that wen the FLUIE was moving in the continuous pattern, its torque was maintained by the Large field system…wich made its surroundings appear blurred and without ny apparent change in them.
When u moved towards its hexagon area, it was unfazed cz mybe ur movement wasnt fast enuf to let its small field system respond to changes in the “Apparently” stationary
surroundings! However wen u actually moved into its hexagon,.i.e. u moved into its field of vision of its short field system, wich discriminated a new object from its background…. thats wen u elicited a sudden response of turning away from it! so it immediately moved aside but started following the same original pattern wen it made ur new position as part of the surroundings again! (ground discrimination task can only be accomplished, if the object and background differ in at least one respect such as in contrast luminiance, colour or retinal velocity). And wen u withdrew urself frm there and moved further back to your original position, FLUIE found no new object inciting a change in its apparently still surroundings and so moved back to the area!!
3. About the positioning of FLUIE at certain height above the ground and returning to same position even wen disturbed by blowing of air frm mouth….and about the fact that it only takes sharp turns and no smooth curves….
Ans: Well for that chek out the mechanism of YAW TORQUE in an airplane, changes in wich are brought about by the deflection of the “rudder” and vertical stabilizer in an airplane and they lead to the changes in direction etc of the plane….its related to the same sort of mechanism in the hovering of insects and their turning!!! very interesting!
4. Why FLUIE was roaming about so ardently in that hexagon….??
Ans: What i think was FLUIE was trying to fix its territory for the prospective mating with a females. According to a few papers i read its said that receptive females of the species prefer resident males to non resident ones! and also any other male if it had come into the territory of FLUIE. it wud have chased him away! dunno hw true this is…but territory defining is definitely an option.