#perlodinae

[jonnysinsectcatalogue]

Stonefly - Subfamily: Perlodinae

With special thanks to a dear friend of mine exploring the wilderness of Squamish, British Columbia, this video is the first (of hopefully many) of 2026. Keeping to their active season of early spring as also recorded in previous videos, the Stoneflies of Squamish have returned and this one is quite active! Although this individual appears to be on dry land, it isn't very far from a water source. Specifically, this insect was filmed near the Squamish River by Edgewater Park; a fine water source spend time developing as an aquatic nymph. According to my friend who recorded this video, the rocks filmed here are occasionally submerged completely by water which arrives in the form of rainfall and meltwater from on snow on B.C.'s mountains. If that's the case, this is the perfect environment for Stonefly nymphs to complete their metamorphosis into a winged adult. They would be able to cling onto these stones or nearby man-made structures when the water rises, and then emerge as it recedes and conditions become warmer and drier. My friend also noted that while the stone parts exposed to the sun were radiating heat, the water was freezing. While such temperatures would be harmful to most insects, Plecopterans can have adaptations against ice cold conditions such as chemicals within their hemolymph (blood) that act as an antifreeze, or even simple strategies such as insulating themselves from cold within riverbed materials. If successful and uneaten, the result is a fit adult Stonefly with energy to spare as it searches for a mate. Although now equipped with braided-veined wings, it usually will not fly far from its emergence site.

Video was recorded on April 9, 2026 in Squamish with an iPhone X. You can find this video on YouTube as of May 3, 2026. While identification is still preliminary, I'm inching towards the identification of this insect and the other Stonefly individuals previously filmed from Squamish. This insect (and the others) might be Skwala americana, more commonly known as the American Springfly. But what do you think? Are there other possibilities?

[jonnysinsectcatalogue]

Stonefly - Subfamily: Perlodinae

The Stoneflies of Squamish are still active! My dear friend sent me another find from the highway bridge near the Mamquam River, and this individual is in much better shape compared to the previous one. This is to say the wings are full and the rear cerci are curved and intact. Hopefully this provides a good example of a typical Plecopteran form and gives a lasting impression of how large the wings can appear. Although the wings are airworthy, the pairs apparently do not operate in unison (unlike more common garden insects) and are quite large despite the moderate size of the Stonefly, leading to clumsy flight for the adult. Fortunately, since these insects don't stray too far from their emergence site, flight isn't a big concern for travel. Moreover, it has come to my attention that Stoneflies and similar aquatic insects (e.g. Fishflies and Mayflies) may rely on skimming across water to travel. By placing their abdomens and/or legs on the water's surface, the muscle load on the wings is reduced, the weight carried by the wings is lessened and the wings don't need to beat as much during flight. Observations like this have led to examinations of wing evolution in aquatic insects and theories that ancestors (of these aquatic insects) relied on skimming to supplement flights made with smaller, less developed wings and overall weaker muscles. Don't be fooled, however, this Stonefly can indeed fly.

Video was recorded on April 7, 2024 in Squamish with an iPhone X. You can also find this video on YouTube now as of June 29, 2025 as part of a larger video. For additional information, I recommend the following papers by Marden J. H. et al.: Surface-Skimming Stoneflies (1994) and Surface‐Skimming Stoneflies and Mayflies (2000). The former paper was brought to my attention by the YouTube channel "Ant Lab" after watching an upload that captured slow motion Stonefly, Mayfly and Fishfly take-off and flight (at 3200 FPS). If that sounds interesting to you, you can watch that video as well.

[jonnysinsectcatalogue]

Stonefly - Subfamily: Perlodinae

Not only did my dear friend out in Squamish send me pictures of a new order of insect, but he also sent me video of the specimen. This Stonefly was found at a highway bridge near Mamquam River, a great eagle-spotting location during the day if you don't mind the noise of traffic, and it seems a great location to find Stoneflies. Many external observations suggest that concrete bridges and artificial wood structures near flowing water are ideal places to find nocturnal Stoneflies emerging as adults (I tend to find Caddisflies instead). Moreover, they seem to be attracted to lights, and this individual certainly was, so much so it tumbled off the railing! Even after falling, it was very persistent! I'm very fascinated by how the legs become longer and thicker as you go down the body; likely an adaptation from the naiad stage, clinging to rocks. But now, above water, they can fly, but Stoneflies in general aren't strong fliers. This individual would have very great difficulty taking to the air with a broken wing. Hopefully chance smiles upon it to find food and/or mate. The former varies from specie to specie: some Stonefly adults will not eat while others will eat pollen or debris. In all cases, they do have chewing mouthparts, but it's interesting how only some choose to chew. This may be an adaptation centered on emergence time. Perhaps early spring emergent species focus on finding mates rather than focusing on food as pollen-rich flowers may be scarce.

Video was recorded on March 15, 2024 in Squamish with an iPhone X. As well, observe these river beauties carefully. With those long hind cerci and flattened bodies, a sudden glance may mistaken them for Earwigs. You can also find this video on YouTube now as of June 29, 2025 as part of a larger video.

[jonnysinsectcatalogue]

Stonefly - Subfamily: Perlodinae

With special thanks to a dear friend of mine currently in Squamish, another new insect order can now be described on this blog. Joining the insect is the order "Plecoptera". These insects are typically flat-bodied with large membranous wings folded over their back. Many species have cerci protruding from their abdomen and the winged adults are found in close proximity to water. The reason being is primarily two-fold: they spend their time as a predaceous nymph (called a naiad) in water and they are relatively weak fliers (despite their large wings) meaning they won't venture too far from their spot of emergence. At most, they might travel a short distance and search for a mate. Species like this are more commonly known as Stoneflies. With a description like this, they are quite similar to other water-associated insects that gain wings and leave the water as adults such as Alderflies, Mayflies and Caddisflies. However, once you learn the exact shape and construction of their bodies, you'll never mistaken one of these for something else. Even Fishflies are distinguishable given their unbelievable large wings! The common name "Stonefly" apparently arose from a behavior at their armored naiad stage: they cling to large stones as they live underwater and try mightily not to get pulled away by the current as they snatch other animals for food (adults are either herbivorous or do not eat at all).

With water currents in mind, it seems to be a miracle that these insects can even hatch without getting pulled away to oblivion. I think that using a current to aid in dispersal is very clever (assuming the locations are suitable). Moreover, Stonefly eggs have a coating that allows them to stick to passing rocks or other pond debris to give them a (hopefully) suitable place to hatch and feed. When pulled from the rock, they will flail downstream aiming to grab another rock, or else become food for passing fish. With this information in mind, it's no wonder this specie is frequently used as fantastic fish bait. I'm not an angler myself, but if an ample source of naiads (not larvae in this case) can be found clinging to rocks, it might be your lucky day. Myself of course, I'd be content seeing the insects in person and later in a photo. Although great fish bait, we should monitor these insects very carefully. Depending on the specie, the naiad stage in the lifecycle of this family of insects can range from 6 months to 3 years (during which there could be as many as 30 naiad molts). With such a long development time, we can't be too hasty to take too much. Secondly, like Caddisflies, Stoneflies cannot tolerate water pollution, making them an indicator of environment quality. A biologically based monitor of the water sounds perfect in my opinion.

Pictures were taken on March 15, 2024 in Squamish with an iPhone X. Happy First day of Spring!