Whats the difference between a skwala and golden stone?

G

golfman65

Guest
#1
Title pretty much says it all..

I've found lots of goldens up north on a river I fish and have asked around but no seems to think skwalas are up there..so wondered what the diff. is?

Here's a shot of a golden I took last Friday..
 

Attachments

Jmills81

The Dude Abides
#2
Traditionally here are some factors that separate

1. Skwalas are usually first of the stones to come off

2. Color, duh!

3. Size variations. Goldens can be big to small...up and down!
 

riseform

Active Member
#3
I thought the following was a great contribution from a recent thread.
Guestimating size from the picture, that nymph looks to be about 2cm (20mm) long. The presence of wing buds would indicate that it should be ready to emerge in the next month or so. According to Hafele and Hilton (Guide to Pacific Northwest Aquatic Invertebrates), yellow stones (Skwala spp.) are 13 - 22mm, about the size of this larva; H2 indicate that the adults are active from April to June, but we know that they emerge as early as March on the Yak. According to H2, golden stones are 25 - 38mm when they emerge after 2 - 3 years as a larva, generally May - August. A key difference between the two is the development of gills. In golden stones, there are thickly-branched filamentous gills at the base of each leg. Yellow stone species either lack these gills or have simple fingerlike gills under the head or base of the legs. Of course, we can't see any of that. Someone with more experience could do the definitive ID from the picture that Matt supplied.

Steve
 

Jergens

AKA Joe Willauer
#4
Traditionally here are some factors that separate

1. Skwalas are usually first of the stones to come off

2. Color, duh!

3. Size variations. Goldens can be big to small...up and down!
I'll add to this.

1. Skwala's do typically come off first, agreed.

2. Skawal's range from tan to dark greyish to olive, with a lighter underbelly than back. Goldenstones typically are a yellowish/orangeish hue.

3. Both bugs vary in size substantially among the species. Goldens are typically bigger, but from my experience, not much. The biggest indicator for me, other than the time of year, which is about 1.5 month difference where i'm usually fishing, is the color, goldens are really that, golden colored.
 

Itchy Dog

Some call me Kirk Werner
#5
I found both under rocks on the Yak this past Tuesday. These ones happened to be nearly identical in size (about a half inch long head to butt, not including the tails), but the underbelly of the Skwalas were very much olive whereas the Goldens were very yellow/gold. Interestingly, both had visible wings, but were still in hiding.
Saw no adults all day.
 

Preston

Active Member
#6
Skwala stoneflies hatch most commonly from mid-February through mid-April and, at least locally, tend to be dark, from a sooty black through a dark olive. They sometimes exhibit yellow markings on the underside of the thorax and abdomen. Golden stones rarely hatch before May and tend to range in color from brown to yellow. Although there isn't a great deal of difference in size, goldens do tend to be a bit larger than Skwalas. I tie most of my Skwalas on 2x-long size 8 dry fly hooks but would go up to a 6 for goldens. From the one picture that was clear enough, I'd say what you were looking at were Skwalas.
 
#7
I'm not so sure your picture is not of a Skwala...check out this picture that is of an adult Skwala. Notice the yellowish line in the center of the pronotum and mesonotum. While this definately isn't a characteristic used to distinguish between the species, I believe goldens have a more vermiculated pro and mesontum. However, one characteristic that is used to distinguish between the subfamily Perlodinae (which the genus Skwala is in), and the subfamily Isoperlinae (which the genus Hesperoperla and Calineuria are in (and is the genuses of the Golden Stones)) is the presence of supplementary veins in the R1 - Rs space. The Skwala in the picture I have attached have these supplemental veins present. Unfortunately, the R1-Rs space in the picture from the original poster is in the shade and I cannot tell if there are supplementary veins. Maybe if there was another picture....?

The colors on Skwala's can vary so much that they could easily be confused with Golden stones, while the Golden stones colors do not vary quite as much..most are golden/golden orange/golden tan. Skwalas on the other hand can range from almost black, to olive to light tan. Also, the lower end of the size range of Goldens definately overlaps with the larger end of the size range of Skwalas. Pretty much just repeating here what Jergens said. I would say the largest Goldens are a size 6 though, so they are not that much larger than the largest Skwala.

Anyways, probably too much info....Any thoughts?

James:beer2:
 

Attachments

Dizane

Coast to Coast
#8
The pics in the OP look Skwalas to me. Like others have said, the Goldens I've seen really are golden/tannish. The dark color of the bug and the yellow around the thorax and leg joints in the OP is consistent with Skwala IMO. I actually tie my Skwala patterns with yellow/black barred rubber legs to mimick the look seen in the OP's pic.

Of course, confusion between Skwalas and Goldens isn't anything new. Anybody who's read Steve Probasco's Yakima River Journal knows about the great March Golden Stone hatch on the Yak.;)
 

Taxon

Moderator
Staff member
#10
James-

... However, one characteristic that is used to distinguish between the subfamily Perlodinae (which the genus Skwala is in), and the subfamily Isoperlinae (which the genus Hesperoperla and Calineuria are in (and is the genuses of the Golden Stones)) ...
Genera Calineuria and Hesperoperla are in Subfamily Acroneuriinae of Family Perlidae (Common Stoneflies).

Genus Skwala is in Subfamily Perlodinae of Family Perlodidae (Patterned Stoneflies).

This can be visualized somewhat easier on Stonefly Taxonomic Structure.
 

Taxon

Moderator
Staff member
#12
You're welcome, Itchy. Seeing your quote made me recognize my fat fingers had dropped a letter in Hesperoperla, but I have fixed it now.
 
#13
You are right guys...my mistake. Correct taxanomic nomenclature:

Skwala:

Order:plecoptera
Suborder:Systellognatha
Family:perlodidae
Subfamily:perlodinae
Tribe:Arcynopterygini
Genus:Skwala
Species:americana...and/or possibly curvata

Hesperoperla (Which I guess is the true "Golden Stone")

Order and Suborder same
Family:perlidae
Subfamily: Acroneuriinae
Tribe:Acroneuriini
Genus:Hesperoperla
Species: pacifica

I was flying through my key way too fast...missed a number. Just goes to show you can't believe everything you read on the internet. Thanks for paying close enough attention to catch my error guys.

James:beer2:
 
#14
The easiest way to tell the difference is by relative cerci (tail) length (for adults on the wing). For larva, Perlids have hairy (gills) armpits and a species specific pattern on their head capsule.....Classenia sabulosa has an "M" above the eyes, Acroneuria has a "keyhole". Never seen a Hesperaperla pacifica, but it has it's own failsafe identifying pattern. Chances are, if the perlids are there, the perlodids are too, unless you go far downstream in the drainage.
 

Taxon

Moderator
Staff member
#15
ShowMeFish makes some good points concerning recognition of the stoneflies previously discussed in the thread.

There are only (4) species of Perlids (Common Stones) present in WA, and their head capsules look like this:
--------------------------------------

Calineuria californica (Western Stone)
--------------------------------------

Claassenia sabulosa (Shortwinged Stone)
--------------------------------------

Doroneuria baumanni (Cascades Stone)
--------------------------------------

Hesperoperla pacifica (Golden Stone)
--------------------------------------

On the other hand, there are (29) species of Perlodids (Patterned Stones) present in WA. However, (1) genus and (2) species are more likely than the others to be observed:
--------------------------------------

Skwala americana (American Springfly)
Skwala curvata (Curved Springfly)
--------------------------------------