Purple Flies - Why do they work?

Purple Flies – Why do they work?

Trying to make sense of Purple Fly Patterns

Purple Haze, Purple juju-baetis, Purple pine squirrel leach, Purple Lively’s BFD, Purple Psycho Prince, Purple Joe, Purple Western Soft-Hackle….alright, I’m really tired of typing and reading the word “purple” here. I continue to be perplexed by the effectiveness of so many purple flies because, as far as I’m aware, I’ve never seen a purple aquatic insect. The parachute Purple Haze has been an ace in the whole for me when dealing with picky risers on the Big Horn and Frying Pan. Purple pine squirrel leaches have produced fish after fish on the Grey Reef section of the North Platte, the Purple Psycho Prince is killer on the Arkansas River. I’m sure most of you use one or several purple flies that have proven their utility over time. 

Don’t get me wrong, purple fly patterns don’t seem to work for me ALL of the time, but often times these flies will produce more consistent hook ups than more naturally colored artificial flies. Unfortunately, I have been unable to find a definitive answer as to why this is. 

Purple Fly Explanations

When I ask the question – Why do you think these fish are so readily willing to eat this purple fly? – I often times hear the response that trout and other fish are able to view and perceive a wider range of light wavelengths and ultimately have ultra-violet (UV) vision.  Knowing that purple and then ultra-violet wavelengths are the shortest wavelengths in the visible spectrum AND trout are able to perceive these very short UV wavelengths, I understand the initial rational for this argument. However, just because trout can see purple and ultra-violet shouldn’t necessarily mean that they should want to eat everything of this color. You and I can perceive the color purple but we certainly don’t develop hunger upon seeing it. Furthermore, most of the scientific journals that I have read clearly indicate that a trout’s ability to perceive UV wavelengths dissipates 2 – 3 years after birth, although this ability may temporarily re-emerge during spawning times (See last week’s post on trout vision). If we are to accept this presumption, then the whole theory that trout are extra sensitive to UV light doesn’t hold.

I also read in an article written by Kirk Deeter on the MidCurrent website that shorter light wavelengths may uniquely bend and refract through aquatic environments, ultimately suggesting that this quality has something to do with the attractiveness of purple (and blue). Essentially the purple colored flies may tend to stand out and be more attractive in the fish’s field of vision. I haven’t come across any convincing evidence that this is the case, but it’s certainly plausible. After all, we know that longer wavelengths are absorbed more easily by water and particles in water (which suggests that the color red is not very visible to trout at deeper water depths), so maybe shorter light wavelengths (i.e., purple, ultra-violet) are less readily absorbed by water and are more visible to trout at deeper depths. 

Another similar explanation is simply the novelty of the fly color. Let me give an example to better explain…. Let’s say there is a dense BWO hatch and trout are literally viewing a hundred bwo nymphs/emergers per minute that are a dark olive/brown/blackish color. As expected, the trout continue to gorge on this abundance of BWOs that are floating in the drift. When you drift your artificial hatch matcher in the trout’s feeding lane, he may eat your fly OR he may eat the other 5 BWO nymphs/emergers that are passing by at the same time. However, if you put on a purple jujubaetis that is nearly the exact same profile and size, but is a distinct purple color, this may catch the fish’s attention and trigger a take. I guess this is essentially stating that purple flies are simply attractor flies, which may, in fact, be the answer to this question. 

The bottom line is that I’m not sure what the answer is, but I know purple flies have a special place in my fly boxes. Feel free to post any facts, opinions, or thoughts that you may have on the subject!



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