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Insects Active in Winter

Snow Flies Appearing

1-29-18 snow fly IMG_9481It always comes as a surprise to see tiny creatures moving nimbly over the surface of the snow. However, there are quite a few insects and spiders that do, thanks to the glycerol that they produce in their body fluids that keep them from freezing. The Snow Fly (Chionea sp.) is a type of wingless crane fly.  Most likely its lack of wings is due to the fact that at sub-freezing temperatures it would be very hard to generate enough energy for maintaining flight muscles. They (along with other flies, mosquitoes and gnats) do have two vestigial wings called halteres, the little knobs on the fly’s thorax. They inform true flies about the rotation of their body during flight, and are thought to act as sensory organs for the flightless Snow Flies.

Throughout most of the year Snow Flies can be found in leaf litter, but come winter the adults emerge, mate and lay up to 200 eggs. The lack of predators such as dragonflies and most insect-eating birds makes winter a relatively safe time for Snow Flies to be out and about. Their life span is about two months, during which time they drink by pressing their proboscis against the snow, but they don’t eat.   (Snow Fly in photograph is a female, measuring less than ½”.)

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Wingless Snow-walking Crane Flies

3-2-17-snow-walking-wingless-crane-fly-img_9477Thanks to a sharp-eyed Naturally Curious blog reader, a recently mis-identified active winter insect can be correctly identified. What I referred to as a “snow scorpionfly” last week was, in fact, a type of crane fly that, as an adult, has no wings. Like snow scorpionflies, these wingless snow-walking crane flies appear on top of the snow on warm winter days. These two kinds of insects are also very similar in shape and size, but, unlike snow scorpionflies, this group of crane flies have what are called halteres, knobbed filaments which act as balancing organs (see photo).

Scorpion snowflies, despite their name, are not true flies in the order Diptera.  Crane flies are.  Most species of true flies have one pair of wings, instead of the usual two that winged insects have, as well as halters, which take the place of hind wings and vibrate during flight. While wingless snow-walking crane flies lack a pair of wings, they do possess halteres, which are the key to distinguishing between a wingless snow-walking crane fly and a snow scorpionfly, which lacks them!  (Thanks to Jay Lehtinen for photo I.D.)

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Snow Scorpionflies Active

2-15-17-snow-scorpionfly-039On mild winter days you may wish to look closely at all the dark, little specks on the surface of the snow. Most of them will be bits of lichen, seeds or pieces of bark, but with luck you may find one or more of them moving. Active winter insects aren’t plentiful, but they do exist.

Scorpionflies are fairly common and can be recognized by their long beaks ending in visible mouthparts. (They get their name from one family of scorpionflies that possesses a scorpion-like tail.)  Snow Scorpionflies belong to a family of small, flightless insects, of which there are two species in the Northeast. They only measure about 2/10’s of an inch, so careful scrutiny is necessary to spot one. Their dark color and an anti-freeze substance in their blood allows them to remain active to 21°F., during which time they feed on mosses. When startled, Snow Scorpionflies often jump up in the air and land with their legs crumpled up (see insert) looking even more like an inedible speck of dirt. It’s fairly easy to tell their gender, as female Snow Scorpionflies (photo) lack wings, and males have bristly wings adapted for grasping females.

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Stoneflies Drumming

2-22-16 stonefly 019Stoneflies spend the larval stage of their life in streams. When the larvae mature, they crawl out of the streams they grew up in, split their larval skins and emerge as winged adults, ready to mate. Stoneflies are unique among aquatic insects in that there are different species that emerge in all months of the year. Most species mature in warmer months, but some do so during warm spells in winter and there are two families (referred to as winter stoneflies) that emerge only at this time of year, perhaps because of the scarcity of predators.

Recently, perhaps due to the warm weather this past weekend, large numbers of stoneflies  emerged. In places, the snowy banks of open streams were littered with half-inch adult stoneflies whose new skins were drying.  This entomological exodus from the water typically takes place at night, to avoid being eaten by terrestrial insectivores and birds.  After their adult skin dries, winter stoneflies can be seen crawling on top of the snow as they search for a mate.

In many species, male and females locate each other by tapping the tip of their abdomen upon the substrate, a process referred to as “drumming.” Any stoneflies in contact with that substrate will feel the vibrations of this drumming. Male and female drumming patterns are specific for each species and for each sex. Male stoneflies initiate drumming and females answer. This means of auditory communication is closely related to the “songs” of crickets, grasshoppers and katydids. The difference is that the sound waves of the terrestrial insect songs travel through the air and are loud enough for humans to hear, whereas the sound waves of stonefly drumming travels through a solid medium and is inaudible to us.

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Waxwings Supplementing Sugary Fruit Diet With High-Protein Insects

4-3-15 bohemian waxwing IMG_2383The diet of both Cedar and Bohemian Waxwings is primarily sugary fruits throughout most of year. Research shows that they can subsist on this diet exclusively for as many as 18 days. However, in winter when feeding on fruits, they also feed on buds and available insects. In warmer months, waxwings will fly out over water from exposed perches, much like flycatchers, and snatch emerging aquatic insects such as mosquitoes, midges, mayflies, caddisflies and dragonflies out of the air. They also glean for vegetation-borne insect prey, such as scale insects. At this time of year they are taking advantage of winter stonefly hatches over open streams. (photos: bohemian waxwing & stonefly)

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Exposed Honeybee Colony

honeycomb IMG_5036In the Northeast, honeybees typically choose a protected site such as a hollow tree in which to build their hive. Harsh winters demand this protection. Infrequently you will see where an attempt has been made to survive the elements without anything to contain the heat that the honeybees produce by shivering, or to block the wind, snow or sleet. Inevitably, this far north, the colony does not survive the winter.

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Winter Stoneflies Still Emerging

4-2-14 stonefly 123It seems early, especially with feet of snow still on the ground, to be seeing insects flying around, but some have actually been present all winter. An order of insects (Plecoptera) known as stoneflies spends its youth (one to four years) living in streams before emerging as winged adults. Some of these species, referred to as winter stoneflies, emerge from January through April, providing food for early-returning, insect-eating migrants, such as Eastern Phoebes, Tree Swallows and Red-winged Blackbirds. Stoneflies only live a few weeks, during which time they mate and lay eggs. Some do not feed, and others consume plant material. Because stoneflies are intolerant of polluted water, if you see one it’s a good indication that the water quality of the stream that it came from is excellent.

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Backswimmers Active Under Ice

11-18-13  backswimmers under ice 061Backswimmers are insects classified as “true bugs” and belong to the order Hemiptera. Most Hemipterans are land dwelling, such as stink bugs and assassin bugs, but there are a few, such as water striders, water boatmen and backswimmers, that are aquatic. In the fall, when most insect hatches have ceased, backswimmers come into their own. While some hibernate at the bottom of ponds in winter, others remain active, sculling through the water with their oar-like hind legs that are covered with fine hairs, preying on all forms of life up to the size of a small fish. Thanks to bubbles of oxygen that they obtain from pockets of air just under the ice and carry around with them like mini aqua lungs, backswimmers can continue to stay below the surface of the water for several minutes. Like most aquatic insects, backswimmers supercool their bodies (produce antifreeze compounds called cryprotectants that allow their body fluid to go down to 26 to 19 degrees F. without freezing). Right now, when there’s a thin layer of ice on most ponds and no snow covering it, you might want to peer through the ice at the edge of the pond to see if you can locate any of these cold-hardy creatures. Just be sure you don’t fall in, as I did two seconds after this photograph was taken. My undying gratitude for those of you who have donated to Naturally Curious, as your support enabled me to replace both camera and lens!

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Adult Stoneflies Emerging

7-2-13 stonefly adult 058Stoneflies spend their larval stage on the bottom of streams, in amongst the stones for which they’re named. Some species of larval stoneflies feed on decomposing organic matter, others are predators. As adults, very few stonefly species feed due to their short life span. Those that do feed on algae and lichens, nectar, or pollen. After shedding their skin 10 to 22 times (depending on the species), the larvae crawl out of the water, split their skin a final time and emerge as winged adults. Most emerge in the spring or early summer, though some species mature in the fall, and even in winter. Most larvae spend 10 to 11 months under water, and only 1 to 4 weeks as terrestrial adults. The adults spend their days hiding on the branches or leaves of streamside vegetation, and crawl around at night. They usually only fly to disperse to a new habitat, which is surprising, given the size of their wings.


Goldenrod Ball Gall Fly Larva

3-22-13 goldenrod ball gall fly larva IMG_6182The round “ball” that is often present on the stem of goldenrod plants contains the overwintering larva of a fly (Eurosta solidaginis). A year ago an adult female fly laid an egg in the stem of the goldenrod plant. The egg hatched and the larva proceeded to eat the interior of the stem. As it did so, the larva excreted chemicals which caused the plant to grow abnormally, creating a ball-shaped “gall.” If you were to open a goldenrod ball gall today, you would probably find an overwintering larva (if a downy woodpecker or parasitic wasp hadn’t gotten there before you). Within the next few weeks the larva will pupate, and as early as April the adult fly will emerge from the gall, having crawled out the passageway that it chewed last fall. An inflatable “balloon” on its forehead allows the fly to burst through the remaining outermost layer of tissue at the end of the passageway. The adult fly lives about two weeks, just long enough to mate and begin the process all over again.


Mating Flies

3-18-13 mating flies IMG_6645 (2)It’s hard to believe that flies are not only active but mating now, given the snow and low temperatures that Vermont is still experiencing, but these two flies were perched atop coyote scat doing just that. They are in the Heleomyzidae family, whose members are often found in dark or cold places, and are most likely to be encountered in the spring or late fall. There are species associated with caves, mammal burrows, carrion and birds’ nests, in addition to scat.


Winter Stoneflies Emerging and Mating

3-4-13 stonefly IMG_5015Stoneflies spend the larval stage of their life in streams, but as adults they are terrestrial. When the larvae mature, they leave the streams they grew up in, split their larval skins and emerge as winged adults, ready to mate. Most species mature in warmer months, but there are two families, referred to as winter stoneflies, that emerge at this time of year, perhaps because of the scarcity of predators. You can often find these cold-hardy stoneflies crawling around on top of the snow near streams.


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If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

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Bruce Spanworm Moths Flying

If you’ve walked in New England woods recently, chances are great that you’ve noticed light tan moths with a one-inch wing span flitting about — an odd sight for this late in the year. These are male Bruce Spanworm Moths (Operophtera bruceata), also called Winter Moths, as the adults are active from October to December. They belong to the Geometer family of moths, the second largest family of moths in North America, which includes many agricultural and forest pests. The males are seeking wingless, and therefore flightless, females to mate with. Eggs are laid in the fall, hatch in the spring, the larvae pupate in the summer, and emerge as adult moths in the fall. Bruce Spanworm larvae periodically defoliate hardwood trees, preferring the buds and leaves of sugar maple, American beech and trembling aspen trees.


Insects in Winter

What happens to insects this time of year?  A few remain active, such as snow fleas, and some, like monarch butterflies, migrate, but the vast majority of insects overwinter in New England.  The insects that stay here are susceptible to freezing due to the fact that they cannot control the temperature of their body.  Some insects, such as woolly bear caterpillars, can tolerate having ice form in their tissues, but most insects go into a state known as diapause.  When the days start getting shorter, these insects reduce the water content of their body, as water freezes at a high temperature compared to other liquids, and replace it with glycerol, which acts like antifreeze, protecting them from freezing.  (Due to technical problems which hopefully will be resolved soon, I am unable to include a photograph with this post.  My sincere apologies.)


Honeybee Hives

Rarely do you see or hear about honeybees attempting to construct a hive outdoors that isn’t inside a hollow “bee tree” or in a rock crevice.  Occasionally they do attempt it, but as the empty cells in this exposed comb attest to, honeybees aren’t likely to make it through a Vermont winter without some shelter for their hive, even a winter as mild as the one we just experienced.


Snow Flies

It always comes as a surprise to see tiny creatures moving nimbly over the surface of the snow.  However, there are quite a few insects and spiders that do, thanks to the glycerol that they produce in their body fluids that keep them from freezing.  The Snow Fly (Chionea sp.) is wingless, probably because at sub-freezing temperatures, it would be very hard to generate enough energy for maintaining flight muscles.  They (along with other flies, mosquitoes and gnats) do have two vestigial wings called halteres, the little knobs on the fly’s thorax.  They inform true flies about the rotation of their body during flight, and are thought to act as sensory organs for the flightless Snow Flies.  Throughout most of the year Snow Flies can be found in leaf litter, but come winter the adults emerge, mate and lay up to 200 eggs.  The lack of predators such as dragonflies and most insect-eating birds makes winter a relatively safe time for Snow Flies to be out and about.  Their life span is about two months, during which time they drink by pressing their proboscis against the snow, but don’t eat.   (Snow Fly in photograph is a female, measuring less than ½”.)