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Black-and-Yellow Argiope

What’s Inside A Spider Egg Sac This Time of Year May Surprise You

10-2-17 black and yellow argiobe egg sac2 IMG_5913

Some species of spiders (including wolf and jumping spiders) overwinter as young adults and mate/lay eggs in the spring. Many spiders, however, mate in the fall, after which they lay eggs and die. Their white or tan egg sacs are a familiar sight at this time of year. One might assume that these species overwinter as eggs inside their silken sacs, but this is rarely the case as spider eggs can’t survive being frozen. Spider eggs laid in the fall hatch shortly thereafter and the young spiders spend the winter inside their egg sac.

Although egg sacs provide a degree of shelter (the interior is packed with very fine, very soft silken threads), the newly-hatched spiderlings do have to undergo a process of “cold hardening” in the fall in order to survive the winter. On nights that go down into the 40’s and high 30’s, these young spiders start producing antifreeze compounds, which lower the temperature at which they freeze. By the time freezing temperatures occur, the spiders are equipped to survive the winter inside their egg sac – as spiderlings, not eggs.  (Photos:  Black-and-Yellow Argiope, Black-and-Yellow Argiope egg sac, Black-and-Yellow Argiope spiderlings inside egg sac)

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What’s Inside A Spider’s Egg Sac This Time Of Year May Surprise You!

10-2-17 black and yellow argiobe egg sac2 IMG_5913

Some species of Northeastern spiders (including wolf and jumping spiders) overwinter as young adults and mate/lay eggs in the spring. Many spiders, however, mate in the fall, after which they lay eggs and die. Their white or tan egg sacs are a familiar sight at this time of year. One might assume that these species overwinter as eggs inside their silken sacs but this is rarely the case, as spider eggs can’t survive being frozen. Spider eggs laid in the fall hatch shortly thereafter and spend the winter as young spiders inside their egg sac.

Although egg sacs provide a degree of shelter, the newly-hatched spiderlings do have to undergo a process of “cold hardening” in the fall in order to survive the winter. On nights that go down into the 40’s and high 30’s, these young spiders start producing antifreeze compounds, which lower the temperature at which they freeze. By the time freezing temperatures occur, the spiders are equipped to deal with them throughout the winter – as spiderlings, not eggs.  (Photo: Black-and-Yellow Argiope (Argiope aurantia) egg sac)

 


Wolf Spiders Active

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Wolf spiders can already be seen scurrying around fields, active after a long winter’s nap deep inside tussocks of grass where they stay until the temperature begins to rise.  Some are tiny and black, while others, such as the pictured wolf spider, are larger (1 ½”) and a shade of brown. These spiders hibernate in the winter, but other species have different survival strategies.  Some, like the black-and-yellow argiope, or garden spider, only live one season and die during late fall or winter, leaving behind their egg sac for next season. Many of the more active species that hunt prey rather than trap it in a web, spend the winter as nymphs, or juveniles, becoming full grown in the spring or early summer. In several species of spiders, young spiderlings hatch out in the fall and then remain in a communal egg sac through the winter.

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Jumping Spider Guards Egg Sac

6-5-14 jumping spider2  077Spiders protect their eggs by wrapping them up in a sac they make out of silk. Some species (such as garden, or black-and-yellow argiope, spiders) then die, leaving their egg sac to withstand the elements, as well as potential parasites and predators, on their own. As you would guess, these sacs are usually fairly impenetrable. In other species, female spiders survive long enough to guard their eggs until they hatch, or even until the young spiderlings disperse, and these sacs are usually far less tough. In the species where the female protects her eggs, some females carry their egg sacs with them at all times (wolf spiders, nursery web spiders) while others (jumping spiders) simply remain with the sac. Their excellent eyesight and impressive ability to leap many times their body length gives jumping spiders an advantage over any potential predators. (Photo – jumping spider with egg sac)

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.