Arg... #$%# ! Low Quality. Be careful uploading from phone, the videos were automatically adulterated. Here are the better versions: https://www.youtube.com/watch?v=5cnk5LX1umo https://www.youtube.com/watch?v=YPmUmSZNbu4 Sorry about the double-post, but let me also mention testing on a roadkilled swallowtail wing (with lots of damage) did seem to support the idea that the directional bias follows some biological property. --Brad On Mon, Sep 16, 2019 at 6:11 AM Brad Klee <bradklee@gmail.com> wrote:
Last week, a //Limenitis Arthemis// happened to be in the wrong place at the wrong time, sunning itself near a walking trail between my house and the Physics laboratory. This species is not currently threatened by extinction. There are plenty to observe all around town, so I did not feel too bad about capturing it with my bare hands and paralysing it by the method of thorax pinching. Later I put it into a plastic bag, and killed it by freezing. ( Though it does go against Buddhist vows. ) Students should not be recommend to become "copycat killers". That is a very bad idea.
The purpose of collecting the specimen was to take a closer look at the scales, including an exploratory foray into measuring reflection and transmission. The videos turned out okay:
https://www.youtube.com/watch?v=FrRozvSffqc https://www.youtube.com/watch?v=ldpUEeWwhFE
A scanning procedure along a distal wing cell goes through a reflection sequence--light-dark-light--which supports what we already know, that the iridescent photonic structures are more reflective than the dyed-black scales. The body and tracheal tubes are also very reflective, leading to quite a nice light show. Comparatively, scattering from iridescent scales is more dispersive, and scattering from tubes produces tight and interesting curvilinear forms.
We also noticed transmission and diffraction through the wings, so made a second recording. The spot pattern does appear at first glance to be same or similar to the typical sinc-squared function. The data shows a directional bias at about a right angle to the tracheal tubes bounding any particular wing cell. One more hypothesis is that the directional bias *is not* due to bias in damage done to the wings. Though it could be, so we will probably test more later on a few of the roadkill samples.
There are a number of ways this project could be improved: better quantification, more colors, standard intensity, LED illumination, spectrometry, theory and calculation, etc...
"Light from Orion's stars also reflects off the big fat moon of September, barely noticeable photons, unless you've already killed a little Arthemis, on the battlefield where the sun says I hate you."
--Brad