Winter in the Northern Hemisphere – is there anything more unpleasant? To most entomologists living in temperate climates winter is synonymous with the disappearance of everything they love: insect activity and the pleasant buzz of millions of wings, vibrant colors of plants, warm weather. Our beloved animals have long turned to dust, buried themselves into the ground, or entered a stupor so deep that they might as well be dead. It will be long months before the word “green” re-enters our vocabulary, and both our skin and the ground below our feet breathe a sigh of relief.
But as I walked from my car to work this morning, trying with all my might not to expose any unnecessary fragment of my body to the frigid, dry air, I suddenly remembered that there was an insect, a very interesting one, that flourished in this dead season. I first saw it a few years ago in the middle of February on Wachusett Mountain in MA, jumping on the surface of deep snow like a black, shiny flea. It was a snow scorpionfly, a fascinating insect that up that point was only familiar to me from entomology textbooks.
Snow scorpionflies (Boreidae) are fascinating insects that can often be found on snow in temperate forests of the Northern Hemisphere. Their relationships are still somewhat mysterious —traditionally they have been considered a family of scorpionflies (Mecoptera), a group of agile, predaceous insects, but recent molecular and morphological studies suggest that they may be in fact more closely related to parasitic fleas. Regardless of their genetic affinities, these peaceful, moss-feeding creatures resemble little either true scorpionflies or fleas, and both their larvae and adults feed on mosses.
But why are they active in the middle of winter? Bodies of all living cells contain a very high proportion of water, which turns into ice crystals when the temperature falls below 0°C, damaging the cell structure and potentially killing the organism. And yet, even in the middle of winter snow scorpionflies are not alone. Many arthropods have evolved physiological adaptations that allow them to survive and be active in subfreezing temperatures. As ectotherms, animals that cannot generate their own body heat, winter insects and spiders must possess the ability to supercool their body fluids in order to remain active in subfreezing conditions. Supercooling, a process that allows them to lower their body temperature to well below the water’s freezing point and still maintain its liquid state, is achieved by the presence of polyhydric alcohols and antifreeze proteins in their hemolymph and cells.
Like other winter-active insects, snow scorpionflies take advantage of the fact that most predators that target insects disappear in the cold months, and come out in large numbers to mate. The larger and chunkier female is completely wingless, whereas the male has a pair of strangely modified, scissor-like wings, which he uses to clasp the female’s mouthparts and secure her position on his back during mating. After mating the female uses her long, external ovipositor to lay eggs in clumps of moss, where they will stay dormant until spring.
I have not seen scorpionflies this year, yet, but I will look for them. These animals may be about the size of a pinhead, but for me, in this season, they loom large.
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For most of my life I was also among the “why bother going outside in winter, all the insects are dead or underground” camp. Though the past few years I’ve been learning how to find more insects outside during the cold months, and it’s a fun challenge. In fact during the first date with my boyfriend two years ago we took a walk through the woods and I pointed out winter stoneflies, collembola, and reached into a (very cold) stream to pick up caddisfly larvae.
Last year our lab members found some winter scorpionflies, and we’re already planning trips to track them down again this year. It was quite exciting to find them. http://caterpillarblog.com/?s=boreid
Great post! Here’s one I was surprised to see in the winter – a juvenile wolf spider. (http://prairieecologist.com/2010/12/30/photo-of-the-week-december-30-2010/ )
I guess they’re fairly commonly seen in the winter and feed on snow fleas and other little critters. I had no idea, and was surprised at how quickly it was moving on an 18 deg F day.
I am ashamed to say I have never seen a live one, even though they are the mascot for the Entomological Society of British Columbia, where I live. Thanks for showing us such great pictures, with mating and everything! I will redouble my efforts to see some myself this year!
The photographs are doubly amazing when you consider how small these little guys are. Wow!
This is unbelievable! I’m so excited to read this, haha (even after coming in from the 4 degree weather outside)! I am way too bug deprived, although I did get to photograph a stowaway pepper weevil from a jalapeño last week. I hope they can be found in the Berkshires; would love to get some shots. Great photos, as usual, Piotr!
“To most entomologists living in temperate climates winter is synonymous with the disappearance of everything they love” Too true! I doubt I’ll spot any scorpion flies – I’d have to go *outside*, in this weather, to do that! – but it’s cheering to think that they’re out there, none the less. (I usually sustain myself with the thought that the bugs haven’t really disappeared, the next generation is just waiting, in egg form – that there are more little insect embryos this time of year than there are adults in the height of summer. They’re just hidden.)
Scorpionflies are not the only insects active in the middle of winter. This is also the best time to find certain springtails, wingless flies, and even beetles. In fact, when I was photographing the scorpionflies I also saw ants being active on the snow. Still, nothing beats nice, warm, summer weather!