Plastronic Baetis

A Submerger Designed to Look Like a Silvery Plastron on a Sunken Baetis spinner.
The Plastronic Baetis is my take on a silvery fly design that mimics the total reflection of daylight from an air layer, called a plastron, that a Baetis uses to respire as it crawls underwater to lay its eggs. The plastron is held between a spinner's upright wings and also covers its body. The total reflection from the surface of the plastron can obscure the spinner behind this mirror-like layer so that insect's details, like color and segmentation, need not be included in the fly design.

The idea of fishing flashy downwing wet flies and flat-wing spinner patterns after Baetis hatches has been around for decades. After reading several books that mention egg-laying Baetis it seems that my all-silver design is a bit different and perhaps new in that it uses the slot of a silver bead mounted facing forward on the hook to support a single upright silver tinsel wing as well as form the shiny thorax of a Baetis when underwater.

According to Knopp and Cormier (in their book "Mayflies", 1997, Ch. 3), its the larger-size Baetis species of North America (AKA BWO's) -- those mostly size 20 and larger—that use a plastron to respire while they crawl to the stream bottom to deposit their eggs. An exception in the Baetis clan is the so-called tiny BWO's, those species usually much smaller than size 20, that lay eggs on the surface like most other mayflies-- not underwater.

So, these larger size Baetis, made buoyant by the plastron, have a hard time clinging to the bottom, and often drift off (Ralph Cutter, 2005, "Fish Food" p. 81). Trout are known to eat these plastron-coated upwing spinners while they are drifting or while they crawl along underwater. If drifting, their buoyancy tends to make them rise up to the underside of the film: see review by Peter Hayes, 2013, "Fly Fishing Outside the Box", Ch. 16.

These larger Baetis are widely found throughout the world, are a species whose life cycle repeats in few months and thus hatch repeatedly each year. As such they rank near the top of important trout foods for anglers to imitate. The underwater egg-laying phase of these larger BWO's includes at least half the hatch, that is all females (as well as some males!), try to end up as submergers back underwater. The Plastronic Baetis targets the aftermath of this egg-laying—a spent spinner rise if you will—as they release from the steam bottom and drift up.

Recipe:

Hook: Tiemco 206BL sized 16-20

Thread: White 20D Nanosilk

Thorax: represented by a 1.5mm slotted silver tungsten bead. NOTE: Slide bead onto the hook with the slot side facing towards the hook eye and leave it loose near the hook bend. Tie in the thread at the hook eye.

Single Upright Wing: Two strands of silver Hedron Fire-Fly tinsel are repeatedly folded over to make 8 or more segments. The mid-point of the stack of tinsel segments is then lashed on the top of the hook shank about 1/3 of the way back from the hook eye. The bead is slid forward and rotated so the uplifted wing segments can slide into the bead's slot. Secure the bead using tapered wraps of thread on both sides of the bead to build up the thorax. Continue to lash in the wing and force it up and into the bead slot using Figure-8 style wraps over and across the wing in the bead. Trim the wing to about 1.5 times the length of the hook shank as well as cut it at a steep angle towards the rear of the fly like an upwing Baetis. Finally, trim off any tinsel bits that flair outside of the narrow single upwing form.

Single Tail: I use a bundle of about four silvery fibers from a Coq de Leon feather. Set the tail length at least two times the hook shank length (Syl. Nemes, "Spinners" p. 128). It is not necessary to flare the tails: Frank Sawyer ("Nymphs and the Trout", 1958, p. 84) first wrote that Baetis spinner tails are seen to merge together and form a single-looking tail as they crawl underwater.

Abdomen and Head: I now use Sulky metallic silver tinsel 8001 coated by a layer of thin UV cement

Collar: a few light-dun CDC puff fibers

Whip finish
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Thanks to these contributors for permission to use their imagery (listed in order of use):

1) Stroud Water Research Center: video clip of "Mayfly Eggs Hatching a Minute After Being Laid" (https://youtu.be/lVdadAMyf_c)

2) Peter Hayes & Don Stazicker: video clip of Baetis crawling down waders; See Vimeo.com/378123930—from their Kindle Book "The Flies That Trout Prefer" now coming out in 2025 from Coch-Y-Bonddu.

3) Stuart Crofts: https://www.thefloatingfly.com: a) Baetis spinner with a plastron starting to form about its body and wings; and, b) Baetis spinner wings covered by mirror-like plastron

4) Peter Hayes: The silvery-looking Baetis images in his 2013 book "Fly Fishing Outside the Box". Available at: https://www.amazon.co.uk/Peter-Hayes/e/B087QM7Z5Z/ref=ntt_dp_epwbk_1

Chapters:
00:00 Why tie a silvery-looking Baetis?
3:00 Tying a Plastronic Baetis
13:25 Fishing a Plastronic Baetis
14:00 What is a submerger?