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The bizarre world of the supranivean zone (snow insects)

Yesterday was a work day, more or less. I left before the crack of dawn to meet other planning committee members who are involved with organizing Mothapalooza. We spent a good chunk of the day at the Eulett Center in Adams County tightening down various nuts and bolts before opening registration in a few weeks. Special thanks to Mary Ann Barnett for ably overseeing this event, and efficiently running yesterday's meeting. This will be our third Mothapalooza, and you'll not want to miss it. CLICK HERE for a brief recap of the last one. I'll let you know when registration opens.

As I entered the Pike County region on my way south, the landscape transformed into a winter wonderland. A soft blanket of snow capped every twig, branch, and other structure, creating stunning vistas at every turn. Fortunately, I had built in some extra time, and stopped at a particularly photogenic locale to make some landscape images.

The persistent calyces of witch-hazel, Hamamelis virginiana, surrounded by icy snow caps.

After all was said and done with Mothapalooza planning, I joined David and Laura Hughes for what would be a very interesting adventure. Even though we had little more than two hours before dusk settled, we made the most of it and found lots of REALLY WEIRD STUFF.

Our destination was wooded terraces along this creek in the heart of Shawnee State Forest. Several inches of snow covered the ground in most areas, and the temperature hovered around the freezing mark (32 F),
Our targets were animals that live in the supranivean zone. Supra = above; Nivea; Latin for snow. In other words, animals that live on the surface of the snow. Below the snow are scores of subnivean creatures overwintering in the leaf litter and various recesses, sheltered from the exposed elements of weather on the snow's surface. We did not dig down to investigate the subniveans; our goal was to find the ultra tough invertebrates of the supranivean world.

The little black dashes on the snow in the above photo are springtails (species unknown). They were everywhere, scads and scads of them. Perhaps the best known of the winter springtails are the so-called snow fleas; CLICK HERE for a post about those.

A winter stonefly rests on the surface of the snow. Note the tiny springtail between the stonefly's antennae. The stoneflies were quite frequent yesterday.

As always, a trip afield with the Hughes is eye-opening and educational. Both Laura and David have powers of observation that far transcend that of the average person. Their ability to locate strange, interesting, and often ultra-Lilliputian beasts is remarkable. Laura is smitten with aspects of entomology that are poorly known, and she has become nearly encyclopedic in her stores of knowledge. Thanks to her, David and I became quite fired up to find and see the hardy animals presented herein.

A wingless wasp strolls the icy surface. In spite of the cold temperatures, this animal and everything else that we encountered were quite active. While insects may be largely thought of as animals of warm seasons, and most are, there is a trove of six-legged critters for which winter is their season. This wasp is one of the species that forms galls in oaks, either in leaves or sometimes in twigs. They have evolved to emerge and reproduce in the dead of winter.

This is another species of wingless oak gall wasps (presumably; we're unsure of the species). It was truly elfin, measuring perhaps 2-3 millimeters. Because of its constant activity, making photos was quite difficult and most were no good. Photographing small insects on snow is challenging. David and I both shoot with Canon 5D Mark III bodies, and use Canon's uber macro lens, the strange MP-E 65 coupled to twin lite flashes. Nonetheless, imaging scurrying little critters on cold snow and constantly shifting and bouncing light is a challenge. For those of you into photography, I find that in general shooting at ISO 100, f/16, and shutter speed of 1/200 works pretty well. Be prepared to bump up the flash intensity significantly as well.

David found this jumping spider, which really surprised us. It was out and active, and one has to wonder if certain predators such as this have also evolved physiological mechanisms that allow them to hunt in conditions far colder than most of their brethren can withstand. If this jumper was indeed hunting, it would appear to have little competition for the scores of stoneflies and other insects on the snow's surface.

And now for the most bizarre of our finds, and an insect that was high on Laura's wish list. Our quarry was a small and poorly known group of winter insects whose larvae - and adults, perhaps - feed on mosses. We spent most of our time hunting and pecking in areas that had plenty of mosses exposed among the snow.

Suddenly Laura let out an excited yell - she had found a snow scorpionfly! If you have any interest in bugs, it isn't hard to see why she - and us - wanted to find one of these things. Bizarre doesn't cover it. Note the long beaklike proboscis, proportionately massive goggle eyes, and strange segmented body. This is a male of the species Boreus nivoriundus, and its wings are reduced to odd comblike extensions used to grasp and hold the female during mating. Snow scorpionflies cannot fly, but as we can attest, they can hop like fleas. Indeed, the group is though to be some sort of missing link between fleas and scorpionflies, and they are placed in the Boreidae family.

This is a female snow scorpionfly. There are thought to be about 30 species of snow scorpionflies, and apparently only two of them occur in Ohio. This is a female of the other species that we're known to have, Boreus brumalis. With a big dose of beginner's luck, I suppose, we found both of them on our inaugural snow scorpionfly hunt. Much thanks to Benjamin Coulter, who identified these species for me.

In spite of her strange appearance, this snow scorpionfly is visually interesting. Her body looks as if it is forged from polished bronze, and she sports a formidable torpedo-like ovipositor. Perhaps she uses that appendage to push her eggs deep into moss beds.

Insects are ectothermic - they cannot generate body heat. In order to prevent the formation of ice crystals within cells, which would spell doom, insects that are exposed to harsh northern winters are supercharged with proteins and chemicals that reduce the freeze point of internal liquids, thus avoiding death by crystallization. Apparently snow scorpionflies and the other animals mentioned in this post have taken the art of supercooling survival to the nth degree.

There are obviously good reasons why some insects emerge in the dead of winter, or they would not have evolved the ability to do so. Possible reasons include predator avoidance - not nearly as many potential enemies would be active in cold air on the snow's surface. However, as the jumping spider potentially demonstrates, there are probably some enemies afoot. Rare indeed would be the situation where a large crop of food is readily available, and no one is there to plunder.

The snow's surface is also a great "single's bar". It would seem to be very easy for males and females to find one another on the stark white surface. There may also be food sources available that wouldn't be present at other times of the year. Also, a winter emergence might allow the insect to lock up its eggs and/or larvae in well concealed places during the rush of the warm seasons, when legions of predators are active.


Lisa Greenbow said…
Fascinating. I didn't know there were so many wintery insects. I have seen snow fleas but not any of these other insects. I will be on the look out next snow we get. I wonder if they are active in my garden without snow cover?? I will have to be more observant.
Lisa Rainsong said…
What a fascinating post, and the photos are stunning! These insects are absolutely beautiful, and I really appreciate the opportunity to learn about them here. Thank you for writing about these tiny miracles of winter.
Peter Kleinhenz said…
I had never heard of that scorpionfly. Always impressed with your posts, Jim. Thanks for sharing.
Julia McGuire said…
We had read about snow insects in one of our "nature in winter" books. Now that we're having 50 degree days, it might be time to explore more -- very inspiring post!
Anonymous said…
Fun post to read, learn. Gary Wayne
jerzy.proszynski& said…
I cannot identify the displayed American jukping spider, but can comment onenvironmental group of spiders (genera Sitticus, Euophrys) living in nival zone of Himalayas and other High Central Asian mountains, apparently from about 4000 to above 6700 m above sea level. The temperature near surface of snow and glaciers may be quite high, up to 70 degrees Centigrades, the food is abundant - thousands of lower altitude insects lifted from warm valleys and deposited, stunned, on snow fields. The only conditios for spiders living at that height is to be resistant to cold during nights. Search more in Russian ecological literature.
Jerzy Prószyński

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