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Insect Overwintering Habits And Ecology

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      This article deals with the habits and survival strategies of insects during the fall and winter months, where they overwinter, how they overwinter, and how they re-animate when conditions become more favorable. Most insects either migrate or hibernate but it would be far beyond the scope of this article to list all that migrate and/or all that hibernate. Instead, the article will cover some of the more common species.
      This article is geared toward the average amateur interested in insects and is in no way intended to replace or dispute authoritative papers, books, or guides. Instead, it's function is to help educate and inform people who visit BugGuide who might benefit from numerous online references, books, and research that have gone into the making of this article. Although the article is geared more for amateurs it does go in depth on certain topics but the overall context should be readily understandable by the average person.


Words shown in green are included in the definitions in this article.
Other words in blue are linked to items within this article, BugGuide pictures, glossary, or info. Just click on it to view that page and/or information or section within this article.

                                                                                                                                                                                                             

TABLE OF CONTENTS

   * LIFE CYCLE VARIATIONS
   * THE FAT BODY
   * OTHER SENSE ORGANS
   * BODY TEMPERATURE
   * SUPERCOOLING
   * MIGRATION
   * OVERWINTERING LOCATIONS and HABITS of some common species
   * BugGuide DOCUMENTED OVERWINTERERS
   * DEFINITIONS
   * REFERENCES
   * REVISIONS

   * BugGuide GLOSSARY

   * NOAA Climate Data
This gives a national map with some of the more prominent areas and cities linked. So, you should be able to get close to your area. Once you get there you can navigate using the left menu or the tabbed menu above. You can get such things as current conditions, forecasts, and, what I was after, past data. For example, you can get info for every day of last month, or the month before, or five years ago.

                                                                                                                                                                                                             

LIFE CYCLE VARIATIONS
      Life cycles of insects are fairly variable among different insect species, especially where climatic changes are concerned. Many insects go into what is known as diapause, which is a type of hibernation, through the winter months, while others migrate to warmer regions and still others tolerate the cold and wait out the winter utilizing warming techniques and/or sheltering.
      Insects can overwinter in any stage of their development, such as eggs, larvae, pupae, nymphs, or adults, unless they migrate. Most insects have a single generation life cycle but there are some that require two or more years to fully develop. So, they can be found in any or all stages of their life cycle during overwintering. Life cycles are not paramount in all insect overwintering but things such as environmental temperature and length of day are and are the major factors involved in sending an insect into diapause or causing them to migrate. Usually only one stage of development is involved in diapause. In other words, if an insect enters diapause as a nymph then it will come out of diapause and emerge the following spring as a nymph. But, some insects will go through two or more stages during overwintering, such as the Codling moth where individuals of the first generation pupate and emerge as adults in the summer, but individuals of the second generation in autumn don't. The larvae of the second generation will remain as larvae in silk-lined cells under the bark of apple trees unless subjected to a short period (approximately three weeks) of low temperatures ((0°C (32°F) or lower). When returned to normal developmental temperatures, they pupate and complete their development. Another example is the Mexican Bean Beetle, which will breed continuously throughout the year if conditions are favorable, but will hibernate as an adult for several months if subjected to low temperatures ((3°C (37.39°F) or lower).
      There are many places where an insect can overwinter. They include, but aren't limited to, under rocks, in or under fallen trees or limbs, in leaf litter, under dead plants or grasses, in burrows, in holes dug into the side of a tree, under tree bark, or in the "folds" of tree bark. Typically though, we, as humans, usually see them in winter when they get into our houses or buildings. Although it is common for insects to get into a home to overwinter, most times we never know they are there. They get in spaces of windows or doors, in between walls, in attics, in cellars or basements, under porches or decks, in storage sheds, or just about anywhere they can get out of the weather. Once they get inside they will sometimes maneuver to a warmer section of the house and, in doing so, can expose themselves out in the open where we can see them. If the weather becomes variable (discussed later), which is when there are unusually warm days during the winter, they can come out of diapause and roam around. If they are inside when this happens we will see them then too, trying to get back outside. When the climate is unstable in this way it is very hard on overwintering insects and the mortality rate increases, especially if this happens several times during diapause.
      The problem of climate variability is a factor, especially for insects that use chemicals to stave off the cold or control internal ice crystallization. These insects use glycerols (antifreeze), primarily, to stop ice from forming at the cellular level, as this would destroy tissue and lead to death. The problem is that when the temperature rises enough to bring them out of diapause then their body essentially thinks it's spring and they re-animate and wander around searching for food, as opposed to staying dormant the entire winter season, which is the norm. But if this warming trend only lasts a few days then turns cold again the insect will go back into diapause. This is very hard on insects if it happens several times during a winter. It is the equivalent of having multiple winters all in one winter season and many insects can't cope with going in and out of diapause so many times in one year and die off.

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THE FAT BODY
      The fat body is a cluster of cells found in the body cavity. Its location and degree of compactness varies in different insects. It serves as a food storage reservior and is important for intermediate metabolism. It's best developed in the late nymphal or larval instars. By the end of metamorphosis it is usually depleted. But, some adult insects that don't feed keep their fat body in adult life and actually live off of it until it's gone.

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OTHER SENSE ORGANS
      Insects usually have a well-developed temperature sense. The sense organs they use are located all over the body, but are more numerous on the antennae and legs. It's probable that these organs are specialized thermal receptors. Some insects have a well-developed humidity sense, but not much is known of the sensory mechanism involved.

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BODY TEMPERATURE
      Insects are usually considered to be cold-blooded, meaning that their body temperature rises and falls with the outside temperature. This is the case with most insects, especially if they aren't very active, but the action of the thoracic muscles in flight usually raises the insect's temperature above that of the surrounding environment. The cooling of a small insect is fairly quick, and the body temperature of a small insect in flight is very close to that of it's surroundings. In insects like butterflies and grasshoppers the body temperature in flight may be 5 or 10°C (41 to 50°F) above the surrounding temperature, and in insects such as moths and bumble bees (which are insulated with scales and/or hair), the metabolism during flight may raise the temperature of the flight muscles 20 or 30°C (68 to 86°F) above the environmental temperature. Wow! Honey bees also use this same tactic when confronted with an enemy, such as a hornet. Certain hornets attack honey bee hives to steal their food and pupae. Usually there will be a hornet scout that will find the nest then return later with the others to raid the hive. If the honey bees can isolate the hornet scout they will swarm it and essentially cook it alive by vibrating their wings and raising the temperature of their collective to a point that basically kills the hornet with heat, preventing it from revealing their location to the other hornets.
      With most flying insects, the temperature of the flight muscles must be maintained above a certain point in order to produce the power required to fly. Many bigger insects may increase the temperature of their flight muscles before attempting to fly by vibrating their wing muscles.

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SUPERCOOLING
      When colder weather approaches insects that don't migrate either tolerate the cold or utilize freeze avoidance measures. These freeze avoidance measures include avoiding or stopping of intracellular and extracellular freezing. Due to the fact that insects are inherently small they don't contain a lot of water in their bodies so supercooling isn't that much of an issue.
      Supercooling is when water cools below its freezing point without turning to ice. Water has to have a particle, of dust for example, in order for ice to attach to and form crystals. If there is no such particle present then water can cool down to around -38.1°C (-36.58°F) without freezing.
      One way to avoid freezing is for insects to find a completely dry place to overwinter where ice crystallization cannot occur. Some insects also completely empty their gut before going into diapause to eliminate ice crystallization inside the body. Also, many insects change their body's biochemistry by using polyols, such as Glycerol, which acts as antifreeze. Some insects also produce thermal hysteresis proteins that lower supercooling and freezing points and block ice formation by attaching to the surface of forming ice crystals, preventing growth. Freeze tolerant insects use polyols like those seen in freeze avoidant species. Freeze tolerant insects may also use thermal hysteresis proteins to limit the growth of extracellular ice and prevent intracellular freezing.

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MIGRATION
      "Migration" it usually is thought of as the spring and fall flights of birds, where most or all of the individuals of a species fly over a long distance from nesting grounds to overwintering grounds. Or you might think of the great Buffalo migrations that occured in the not-so-distant past of the U.S. in search of greener pastures. Similar mass migrations occur in some species of insects, but with insects the migrations are usually one way, so the migrating insects don't make a return flight. If a return flight is made it's made by the next generation.
      One of the best known of the migrating insects is the Monarch butterfly. The migration of this species has been studied by tagging, in which the tag is a small piece of paper attached to the front edge of the front wing. Thousands of Monarchs have been tagged and enough have been recovered to give an idea of their movements. In late summer the Monarchs that have developed during the summer in the north begin to fly south. The further south they go, the more that their numbers increase, and in some parts of the country huge gatherings of Monarchs are seen on their migration south (see reference picture below this paragraph). Most of these probably go as far south as the southern United States or northern Mexico. The longest flight known for a tagged individual is 1870 miles from Ontario to San Luis Potosi, Mexico, from September 18, 1957, to January 25, 1958. In the south, and on their flight north in the spring, they reproduce, and most of them that reach the northern part of the breeding range are not the same ones that left there at the end of the summer before.

Also see this interesting article on the Monarch's migration timing component here
      Mass migrations of Short-Horned grasshoppers have been known since biblical times, the migrating hordes often contained millions and millions of insects, and eating everything in sight during the flight. Migrations in these insects seems to be caused by a combination of certain weather conditions and a buildup in numbers. These type flights are seldom seen in this country these days, but a hundred years or so ago occured in the plains states. One of these flights was estimated to contain 124 billion insects, and another was estimated to be half a mile high, 100 miles wide, and 300 miles long. WOW!

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OVERWINTERING LOCATIONS and HABITS of some common species

     > Bumble Bee - Genus Bombus
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      The queen bumble bee comes out of diapause each spring to find a new location to build a new nest and start a new colony. The same nest location as last season is rarely used. A suitable place for a nest is usually on the ground, beneath a flat object. An old mouse hole or other empty burrow in the ground is preferred if it is underneath a flat rock, fallen tree, or hollow in a tree but man made objects will also work such as under a deck, front porch, or attic if they have easy access. The hole chosen by the queen is first padded by bits of dry grass, moss, or any such ground litter. The characteristics of a nest site vary among bumble bee species. Once the queen has found a site, she makes wax pots to store food and wax cells and then the eggs are laid. The eggs then hatch into larvae, which cause the wax cells to expand into a clump of brood cells.The larvae need to be fed both nectar and pollen in order to grow and develop.
      The larvae progress through four instars, becoming larger with each molt. At the end of the fourth instar the larvae spin a silk cocoon under the wax covering the brood cell, changing it into a pupal cell. They then undergo an intense period of growth and become pupae. These pupae then eventually develop into adults, that chew their way out of the silk cocoon but they won't leave the colony for at least 24 hours. The entire process from egg to adult bee can take as long as five weeks, depending on the species and the environmental conditions.
      After the emergence of the first or second group of workers, workers take over the foraging and the queen spends most of her time laying more eggs and caring for larvae. The colony grows progressively larger and at some point will begin to produce males and new queens. The point when this occurs varies among species and depends on available resources and the environment. Only fertilized queens can lay eggs that mature into workers and new queens.
      Early in the colony cycle, the queen bumble bee compensates for potential reproductive competition from workers by suppressing their egg-laying by way of physical aggression and pheromonal signals. So, the queen will usually be the mother of all of the first males. Workers eventually begin to lay males later in the season when the queen's ability to suppress their reproduction diminishes.
      New queens and males leave the colony when they mature. Males in particular are driven out by force by the workers. Away from the colony, the new queens and males live off nectar and pollen and spend the night on flowers or in holes. The queens eventually mate and start looking for suitable location for diapause.


     > Wasps - Superfamily Vespoidea
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      Wasps, such as Yellowjackets and Paper wasps which are considered to be social wasps, also overwinter. But, the entire colony doesn't overwinter, only the new fertilized queen does, which is similar to that of Bumble Bees. The workers and old queen die off when the weather starts getting cold and the new queen finds a suitable place to overwinter. The following spring she emerges and finds a new place for a nest, which is not the old nest from last year. She makes a brand new one to start her new colony. So, if you happen to see a Paper wasp nest in winter you don't have to tear it down because they won't be back to it in spring but the new queen may build her new nest in the same vicinity.
      Solitary wasps, such as Cicada Killer wasps create burrows and dig nest cells off of the main tunnel where she will place paralized cicadas, lay an egg on it, then close the cell with dirt. When the eggs hatch they have plenty of food. They overwinter as a larva and pupation occurs in the nest cell. When winter comes the female then dies as no adults overwinter. Spider wasps, Tarantula Hawks, and Mud Daubers use this same tactic to feed their young until they emerge in spring.


     > Multicolored Asian Lady Beetle - Harmonia axyridis
    * - * - * - * - * - * - * - * - * - * - * - * - * - * - * - * - *
    
      Multicolored Asian Lady beetles start hibernating when the months cool off before winter, but they will come out of diapause and can be seen moving around whenever the temperature reaches about 50°F (10°C). Because they use crevices and other cool, dry, confined spaces to hibernate, large numbers may gather inside walls if there is a large enough opening. Sometimes they gather in areas that recieve frequent sunlight trying to warm themselves, so even on fairly cold winter days, some of the hibernating beetles will come out of diapause because of solar heating. These large populations can create problems because they can form swarms and stay in an area for an extended period of time.
      These beetles have the ability to squeeze through very small openings, even through a closed window. About the best way to make sure they don't get into your house is to tape the windows shut so they can't get through any cracks or openings.
      Some common places for hibernation include underneath siding, roof shingles, landscaping timbers, or leaf litter. Some squeeze through cracks and crevices and come indoors. They may gather together in corners of porches, attics, soffits, wall voids, door or window frames, or dark, undisturbed areas inside buildings.
      Mild, sunny winter days can cause them to come out of diapause. Warmth will reach them at different rates, depending on where the lady beetles are inside the building, so they don't all become active at the same time. Once they are awake they would prefer to be outside and try to get there but because they have followed the heat inside previously may have gotten themselves into a situation where they can't get outside and are trapped inside. This is where most people see them indoors.
      There are varying opinions but most evidence suggests that Multicolored Asian Lady beetles do not reproduce indoors. So, all the Lady beetles seen inside during winter and spring entered buildings the previous fall.


     > Boxelder Bug - Genus Boisea
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      Boxelder bugs overwinter as adults in places like houses and other buildings, in cracks or crevices in walls, doors, under windows and around foundations. In the spring females lay small, red eggs on leaves and rocks, and in "folds" in the bark of female boxelder trees. The eggs later hatch into nymphs that are wingless and bright red with some black markings. These young bugs are usually found on low vegetation near boxelder trees until seeds appear on the tree, that they feed on.
      Boxelder bugs are primarily a pest, annoying people by crawling on both outside and inside of houses on warm fall and winter days when the temperature is high enough to temporarily bring them out of diapause. They can also leave an unpleasant odor if stepped on or frightened. They don't reproduce while in diapause or if they temporarily come out of diapause. They may try to feed on house plants but usually don't cause any damage.


     > Ticks - Order Ixodida
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      Ticks apparently do overwinter, despite old wives tales and common belief. Apparently in spring a blood engorged female lays eggs in leaf litter and vegetaion on the ground. I read some reports that say they can lay as many as 5000 eggs at a time but will only do so once she is engorged with blood and has mated. Very small larvae then emerge in early summer and feed on a variety of hosts including small mammals and birds. In the fall they drop off and overwinter as engorged larvae. The next spring the larvae molt (which I never new they molted) into a larger nymph stage which feed on birds and larger mammals this time like deer, dogs, cats, coyotes, wolves, and humans, just to name a few. This is the stage where they are most likely to be transported to new places while attached to the host. Then, the following fall the engorged nymph drops off to the ground where it then becomes an adult. The adults remain active through the fall and on into the milder days of winter. Then the engorged ticks overwinter in leaf litter and ground clutter. However, I read where there have been all three life stages found on medium sized mammals like jack rabbits. Brown dog ticks can be found outdoors in the southern United States during any time of the year, but are found outdoors during the warm months in the northern United States. It is generally believed that this species of tick cannot overwinter in the more northern United States except within a heated structure, such as a human household. Although I've never seen this they have been reported to get between the baseboards, under window moldings, cracks between doors, or in furniture and can be found in these places in any stage of development.


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BugGuide DOCUMENTED OVERWINTERERS
      This section shows some of the varieties of insects, documented here at BugGuide, that you might find overwintering and where, when available, they were found. You will also be able to see some of the various stages that insects can be in while overwintering. It demonstrates the point that just because you don't always see them doesn't mean they aren't there. It also illustrates that the enthusiastic critter hunter can locate any number of insects, at any time of year, in any stage of development, if you know where to look.
      They are grouped by order but then are in no particular sequence within the order. The dates are also listed just to demonstrate the wide range of critters that can be found during the coldest months of winter.

    -----Beetles

1.January 7, 2008    2.December 25, 2007

3.December 21, 2007    4.December 21, 2007

5.January 20, 2008    6.January 19, 2008

1. Billbug - Genus Sphenophorus
In diapause. Found under a flat rock on top of a boulder.

2. Multicolored Asian Lady Beetle - Harmonia axyridis
Out roaming on a warm winter day on side of house.

3. Checkered Beetle - Enoclerus ichneumoneus
Hibernating between Pine tree bark "folds".

4. Ground beetle - Family Carabidae
Hibernating under Pine tree bark.

5. Ground beetle - Family Carabidae
In diapause. Found under a rock.

6. Death-watch Beetle - Family Anobiidae
Emerged from an acorn.

    -----Bugs

1.January 6, 2008    2.December 29, 2007

3.December 25, 2007    4.December 24, 2007

5.January 27, 2008    6.January 3, 2004

1. Stink Bug - Genus Banasa
Found in leaf litter.

2. Broad-headed Bug - Family Rhyparochromidae
Found under a rock together with another individual.
They were very lethargic. In partial diapause.

3. Leaf-Footed Bug - Genus Acanthocephala
In diapause. Found under a rock.

4. Seed Bug - Genus Kleidocerys
Out on warm day.

5. Green Stink Bug - Species Acrosternum hilare
It was under an old decomposing piece of a tree.

6. Assassin Bug Nymph - Genus Apiomerus
Found under a log.

    -----Roaches

1.December 24, 2007    2.December 25, 2007

3.January 27, 2008

1. Wood Roach - Genus Parcoblatta
Found under a rock.

2. Blattellidae egg case
Found under a rock.

3. Wood Roach - Genus Parcoblatta
Found under a piece of fallen tree.

    -----Pillbugs

1.January 7, 2008    2.February 3, 2008

1. Pillbugs - Family Armadillidiidae
Under a rock between smaller rocks.

2. Pillbugs - Family Armadillidiidae
Found under old piece of tree.

    -----Bees

1.November 7, 2006    2.July 16, 2006

3.November 14, 2007

1. Honey Bees - Species Apis mellifera
In hole in dead tree.

2. Honey Bees - Species Apis mellifera
Hive in floor of office trailer.
I know this isn't in winter but added just to show the kinds of places they can be found.

3. Sweat Bee - Genus Lasioglossum
"There were a large number of these on this plant and they would all disappear and then reappear later. The weather was very warm with temps in the upper 70's and very windy."
"The next day.....
a cold front moved through the area and dropped temps down into the upper 40's. Didn't see any more after that."

    -----Wasps

1.December 21, 2007    2.December 21, 2007

3.December 19, 2007

4.November 22, 2007    5.February 3, 2008

1. Scelionid wasps - Family Scelionidae
Hibernating under pine tree bark.

2. Chalcid Wasps - Genus Brachymeria
Hibernating under pine tree bark.

3. Cuckoo Wasp - Family Bethylidae
Hibernating under pine tree bark.

4. Southern Yellowjacket - Species Vespula squamosa
In diapause.
I turned over a rock and this wasp was clinging to the underside of the rock.
It was in sandy soil and where it had been under the rock there was a shallow
hole for it to fit in. It was very lethargic, I assume due to the cold (high 30F low 40F).

5. Southern Yellowjacket - Species Vespula squamosa
In diapause.
Found under a piece of old dead tree.

    -----Flies

1.January 7, 2008    2.December 30, 2007

3.December 3, 2007    4.December 24, 2007

5.December 18, 2006

1. Crane Fly larva - Genus Tipula
Found under a rock.

2. Golden Dung Fly - Scathophaga stercoraria
Out on warm day.

3. Flesh Fly - Genus Sarcophaga
Out on a cold night.

4. Blow Fly (Green-Bottle) - Family Calliphoridae
Out on a warm day.

5. Vinegar Fly - Species Chymomyza amoena
"Found several inside a closed deli container full of acorns I had gathered to see what might emerge from them. So far I have gathered four apparent weevil larvae in addition to these flies."

    -----Ants

1.December 21, 2007    2.January 7, 2008

3.January 7, 2008

1. Carpenter Ants - Genus Camponotus
Hibernating under pine tree bark.

2. Subfamily Ponerinae
Found under a rock. Didn't see any others.

3. Big-Headed Ants - Genus Pheidole
Colony under a rock.

    -----Termites

1.January 20, 2008

1. Subterranean Termites - Genus Reticulitermes
Found under a rock in trenches/tunnels..

    -----Spiders

1.December 20, 2007    2.December 18, 2007

3.November 28, 2007    4.January 13, 2008

5.January 6, 2008

1. Wolf Spider - Family Lycosidae
Running around in the house.

2. Common House Spider - Species Achaearanea tepidariorum
Out around the house.
Today is 01/15/2007 and I'm still seeing these.

3. Spitting Spider - Genus Scytodes
On the outside of the house.

4. Crab Spider - Genus Xysticus
Shown with larval prey. Found on the underside of a rock.

5. Nursery Web Spider - Species Pisaurina mira
Found in leaf litter.

    -----Harvestmen

1.January 27, 2008

1. Harvestman - Order Opiliones
Found under part of an old fallen tree.

    -----Crickets

1.January 7, 2008    2.November 28, 2007

1. Field Cricket - Genus Gryllus
Found under a rock.

2. Greenhouse Camel Cricket - Species Diestrammena asynamora
On the side of the house on a cold night.

    -----Grasshoppers

1.December 24, 2007    2.January 27, 2008

1. Northern Green-striped Grasshopper nymph - Species Chortophaga viridifasciata
Out on a warm day in Bluestem, Johnson grass, and leaf litter.

2. Northern Green-striped Grasshopper nymph - Species Chortophaga viridifasciata
Found in leaf litter.

Here is another BugGuide article that discusses Overwintering Grasshopper Nymphs that I found pretty interesting also.

    -----Butterflies

1.January 25, 2005

1. American Snout Butterfly - Species Libytheana carinenta
Out on a warm day.

    -----Moths

1.December 29, 2007    2.December 27, 2007

3.January 20, 2008

4.January 27, 2008

1. Tent Caterpillar (Lappet Moth) egg mass - Lasiocampidae
Found on a limb of a plum tree.

2. Moth - Species Pyroderces badia
"This moth emerged from a coast live oak acorn I collected in November and kept in my (heated) house."

3. Tortricid Moth caterpillar - Family Tortricidae
The acorn this critter was in had a small hole on the outside. The part of the acorn seen in this pic is the section that came off empty when I cracked it open. The part with the meat of the nut (or what was left of it) was in the other half.

4. Tortricid Moth caterpillar - Family Tortricidae
I collected a bunch of acorns to see if I could figure out just by looking at an acorn if it had something in it. Notice in the first pic the acorn has a hole in it but it has been resealed from the inside. The second pic shows the caterpillar after I cracked it open and you can also see the hole sealed from the inside. The third pic shows an acorn with a hole but not sealed. Every acorn I collected that had the sealed hole had one of these caterpillars in it but the ones where the hole wasn't sealed had nothing.

    -----Springtails

1.December 19, 2007    2.February 22, 2007

1. Pogonognathellus flavescens
Out roaming at night.

2. Snow Flea - Species Hypogastrura nivicola
Found in the snow by a marsh.

    -----Centipedes and Millipedes

1.February 25, 2007    2.February 18, 2007

3.February 24, 2006

1. Stone Centipede - Order Lithobiomorpha
Found with springtails under a potted plant in the house.

2. Stone Centipede - Order Lithobiomorpha
Found under a log.

3. Millipede - Family Parajulidae
Found under a rock.

                                                                                                                                                                                                             

DEFINITIONS

Overwinter
To survive through the winter months.
Many insects overwinter as adults, pupae, or eggs. This can be done inside buildings, under tree bark, under rocks, or in leaf litter on the ground, and often in our homes or buildings. All such overwintering locations protect the insect from winter weather and cold. Activity almost completely stops until conditions become warmer again. Other insects, such as the Monarch butterfly, some leafhoppers, certain grasshoppers, and several other insect species migrate and overwinter in warmer areas.

Hibernate
A state of intentional regulated stasis usually entered into instinctively at the onset, or just prior to the onset, of cold weather. Animals prepare for hibernation by building up a thick layer of body fat during late summer and fall and some insects do this also.

Dormancy
A period in an insect's life cycle when growth, development, and physical activity is temporarily suspended.

Predictive Dormancy
When an insect enters a dormant phase before the onset of winter conditions.

Consequential Dormancy
When insects enter a dormant phase after winter conditions have begun. This is commonly found in areas with an unpredictable climate, like Oklahoma for example. While very sudden changes in conditions may lead to a high death rate among insects that rely on consequential dormancy, it can be an advantage, as insects remain active longer, and therefore are able to make better use of available resources.

Diapause
Common in insects, allowing them to suspend development during winter months.
"A neurohormonally mediated, dynamic state of low metabolic activity. Associated with this are reduced morphogenesis, increased resistance to environmental extremes, and altered or reduced behavioral activity. Diapause occurs during a genetically determined stage(s) of metamorphosis, and its full expression develops in a species-specific manner, usually in response to a number of environmental stimuli that precede unfavorable conditions. Once diapause has begun, metabolic activity is suppressed even if conditions favorable for development prevail". (Tauber, M.J., Tauber, C.A., Masaki, S. (1986) Seasonal Adaptations of Insects. Oxford University Press).
Entering into and awakening from diapause is usually controlled by the length of daylight hours rather than climatic conditions. This prevents insects from being fooled out of diapause in the middle of the winter by a period of warm weather.

Metabolism
The set of chemical reactions that happen in living creatures in order to maintain life.

Morphogenesis
One of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation. Morphogenesis is concerned with the shapes of tissues, organs and entire creatures and the positions of the various specialized cell types.

Endothermic
Where insects can generate their own heat internally.

Ectothermic
Where insects must rely on external sources to provide their heat.

Freeze Avoidance
An obvious freeze avoidance strategy is migration to a warmer climate. But insects that do not migrate from regions with cold winters rely on either avoiding freezing or tolerating it. Freeze avoidance is the evasion of both intracellular and extracellular freezing. Due to their small size, insects are limited in the amount of water they are able to carry inside their bodies, which results in an ability to supercool quite easily.

Freeze Tolerance
Insects that don’t migrate and are subject to conditions where freezing is inevitable must be able to tolerate frozen tissue. This adaptation is dependent on limiting the presence or location of ice in the body.

Intracellular
Inside the cell.

Extracellular
Outside the cell.

Supercooling
Supercooling is the process where water cools below its freezing point without changing into a solid (ice). Water requires a particle such as dust in order to crystallize. If no particle is introduced, water can cool down to -38.1°C (-36.58°F) without freezing solid. One method of freeze avoidance to select of a dry hibernation site where no ice crystallization from an external source can happen.

Chilling
Cooling without freezing. Used in the context of temperatures above 0°C (32°F).

Polyols
Refers to alcohols containing multiple hydroxyl groups.

Glycerol
A chemical compound. This colorless, odorless, viscous liquid is widely used in pharmaceutical formulas. Also commonly called glycerin or glycerine, it is a sugar alcohol, and is sweet-tasting and of low toxicity.

Cryoprotectant
A substance that is used to protect biological tissue from freezing damage (damage due to ice formation). Serves the same relative function as antifreeze in a car radiator.

Ethylene Glycol
In its pure form, it is an odorless, colorless, syrupy liquid with a sweet taste. Ethylene glycol is toxic, and its accidental ingestion should be considered a medical emergency. The major use of ethylene glycol is as a coolant or antifreeze in, for example, cars and personal computers. Due to its low freezing point, it is also used as a deicing fluid for windshields and aircraft.
(Marchand, Peter (1996). Life in the Cold. Hanover, NH: University Press of New England)

Ice Nucleating Agents (INA)
Chemicals used by insects to promote the freezing of fluids extracellularly rather than intracellularly. In addition to INAs, freeze tolerant insects use polyols like those seen in freeze avoidant species.

Heterodynamic Life Cycle
The adults appear for a limited time during a particular season, and some life stage passes the winter in dormancy or diapause.

Homodynamic Life Cycle
Developement is continuous and there is no regular period of dormancy.

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REFERENCES

   Study Of Insects 4th edition (Borror, DeLong, Triplehorn)

   Wikipedia Insect Winter Ecology

   Wikipedia Supercooling


Back To TABLE OF CONTENTS

                                                                                                                                                                                                             

REVISIONS

01/07/2008 - Revise Wikipedia references to link back to the original articles.
01/08/2008 - Add this revision list.
01/08/2008 - Add NOAA climate link to Table Of Contents.
01/08/2008 - Revise Boxelder Bug info.
01/08/2008 - Revise Multicolored Asian Lady Beetle info.
01/08/2008 - Revise Bumble Bee info.
01/08/2008 - Revise migration info.
01/09/2008 - Revise definitions.
01/09/2008 - Revise sections Body Temperature, Other Sense Organs, Fat Body.
01/09/2008 - Add BugGuide DOCUMENTED OVERWINTERERS.
01/10/2008 - Removed a few definitions as they added no real value to this article.
01/10/2008 - Add some content to BugGuide DOCUMENTED OVERWINTERERS section.
01/14/2007 - Re-write the LIFE CYCLE VARIATIONS and SUPERCOOLING sections.
01/14/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/15/2008 - Revised format of and add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/16/2008 - Revised some formatting
01/16/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/17/2008 - Adjust section title colors to be easier to read.
01/17/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/22/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/22/2008 - Correct an incorrect Celsius temperature in the LIFE CYCLE VARIATIONS section.
01/24/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
01/25/2008 - Add ticks to the OVERWINTERING LOCATIONS and HABITS of some common species.
01/25/2008 - Add wasps to the OVERWINTERING LOCATIONS and HABITS of some common species.
01/28/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
02/03/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.
02/08/2008 - Add content to BugGuide DOCUMENTED OVERWINTERERS section.


                                                                                                                                                                                                             

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