By Christy Solo – ONPA 1st Place Award Winner for Best Local Column
If early blooming flowers are any indication, spring truly is right around the corner, but before we leave winter behind altogether, let’s look at some sturdy stoneflies who are out and about even on our coldest, darkest days.
Meet winter stoneflies (Superfamily Nemouroidea). Here in our area we have two types – regular winter stoneflies (Family Taeniopterygidae) and small winter stoneflies (Family Capniidae).
Of course both types are quite small, but the small winters are actually smaller than the regular winters. You could stack several of either type end-to-end on one of our ginormous (three inch) giant salmonflies.
Winter stoneflies are one-half of an inch in length (13mm), small winters are 10mm (0.4 inches).
Pictured are all small winters and the dime and my hiking boot rivet give a nice perspective of their small-ness.
We’ll focus on the small winters this week because they’re so teeny, tough and cute.
Small winters come by their name honestly. They can be seen in Oregon from November through very early April. Most of the accompanying photos were taken in January, burr!
Why have these tiny titans adapted to cold months when most other arthropods can’t survive?
It’s because small winter nymphs need highly oxygenated water in order to hatch, and winter water has more oxygen. Why? It’s twofold, one, water runs faster in winter which mixes more oxygen in. Also oxygen hogging algae and similar aquatic plants are not as prolific in freezing months.
Small winter nymphs do need aquatic plant matter to grow; that’s their food source. So they’ll do a lot of growing during the warmer months but can only reach full adulthood in winter’s extra cold, clear waters. Nymphs will live in the Rouge (and other streams and rivers with fast moving waters) between one and two years before emerging for their adult molt and taking wing to find a mate.
Once that has been accomplished, females will carry their egg mass, protected under their wings (see photo) and then fly over their home river (creek, etc.) and deposit it directly into the water.
Their time as adults is brief, a week or two. However their short non-aquatic life has nothing to do with the cold temps, they are perfectly adapted to those.
How do they survive? Small winters have a few tricks. They will take advantage of any sun that slips through our gloomy Oregon winters, but for them that’s just bonus heat. They will also take cover in warm pockets, such as under leaves, or even in pockets of ice which are a bit warmer than exposed areas. They’ll also walk on “tiptoe” when it’s snowy or icy to avoid the bulk of their legs and bodies touching ice.
However, their real chilly weather life hack is that they produce their own internal antifreeze. This is made up of compounds such as glycols, sugars and proteins. The colder it gets, the more of these compounds they will produce.
This built-in antifreeze also allows small winters to fly in very cold temperatures. Even early spring flying insects – bee and fly species – are grounded if the temp goes much below 60°.
If you’d like to see a small winter stonefly up close and personal, head to the riparian on any sunny or partially cloudy day from now through March. They love to take advantage of those break-through sunbeams and you can find them on railings, benches or on top of leaves with some consistency. A great excuse to go take a walk around McGregor Park next weekend (weather permitting)!
Final fun fact: Winter stoneflies, both “large” and small are an indicator of good water quality. Lucky for us we have many clear, clean rivers and streams in our area, without those we’d never get to see these bitty beauties with their smoky stained-glass wings.
