Hi David. Several years ago I found that longer legs on my beetle imitations brought more "takes". I fiddled for a bit tying longer and longer legs on the same size beetle body. I made a number of flies with legs that were two, three, even four times longer than patterns available from commercial sources. Fishing them together on a tandem or even triple fly combo, I noticed more strikes on the longer legs. On rare occasions I even had a rising fish switch in mid rise from one beetle to its longer legged partner. Not a scientific study for certain but I do tie longer legs on most of my beetle patterns. Besides, you can always trim them downwards if needed.
I agree with bill on this. However when it comes to the stonefly or girdle bug here I like to cut my tail antennas down more than the rest of the legs. I also try to taper the legs on the abdomen from longer to shorter from head to tail. I also like the legs on the first 3/4 of the body. That being said I don't think it really matters that much and that's one fishy stonefly!
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