An online resource based on the award-winning nature guide

Spiders

Spider Web-filled Fields

10-11-17 spider webs 049A5930While perhaps not as impressive as the square miles of fields and trees that have been totally covered in spider webs in New Zealand, Pakistan, Tasmania and Southern Australia over the past year or two,  New England does have its share of fields adorned with spider silk. The silk in foreign lands was the result of spiders ballooning (floating aloft on gossamer they spin that is lifted by the wind) in spring – an effective means of dispersal. The silk we see highlighted in fields in the early morning dew of autumn in New England serves as webs, or traps, for unsuspecting insects. A majority of these webs are made by grass spiders, many of which weave a horizontal sheet of silk that have a funnel often on one side leading down to a spider hide-a-way. When vibrations alert the spider to a potential meal that is caught in its web, it rushes out, injects the insect with digestive enzymes, and drags it back into its retreat where it begins to feed.

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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)


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)

 


Harvestmen Harvesting

9-15-17 daddy longlegs2 049A3934Like their relatives – spiders, mites, ticks and scorpions – Daddy Longlegs, or Harvestmen, have eight legs (the second, longer, pair of legs are used as antennae). Of all the arachnids, spiders resemble Harvestmen most closely.  However, there are distinct differences between the two orders. Unlike spiders, the two main body sections of Harvestmen are nearly joined and appear as one structure. Harvestmen have no spinnerets nor do they possess poison glands. They also do not have the enzymes spiders have that are capable of breaking down the insides of their prey into liquid. Harvestmen ingest small particles, breaking them down with their chelicerae, or mouthparts, which resemble miniature, toothed lobster claws. One would surmise from this photograph that the legs of flies must lack the nutrition worthy of mastication.

 


Arachnid Anomaly

6-1-17 wolf spider 124

Wolf spiders and nursery web spiders look a lot alike. One way to tell one from the other is to look at the arrangement of the spider’s eyes. Nursery web spiders (family Pisauridae) have two rows of four eyes each, all roughly the same size. Wolf spiders (family Lycosidae) have a row of four small eyes, above which there are two large eyes, with two very small eyes a short distance behind them. From looking at the eyes of the pictured spider, one would assume it was a wolf spider (smallest, topmost eyes are not visible).

However, a second way to distinguish these two families of spiders is to notice how the females carry their egg sacs (the females of both species carry their egg sacs with them wherever they go). Wolf spiders attach their egg sacs to the spinnerets located at the tip of their abdomen, whereas nursery web spiders carry them in their pedipalps (two appendages that look like, but aren’t, legs ) and mouthparts, as seen in this photo.

Thus, this particular spider has wolf spider eye arrangement, and practices a nursery web spider egg sac-carrying technique. My assumption is that this is a mixed up wolf spider or one with tired spinnerets.

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Sheet Web Weavers Still Active

10-9-15 sheet web IMG_5116Spider webs are constructed in a variety of shapes, for which many of them are named. Among others are orb webs, triangle webs, mesh webs and sheet webs. One of the most prevalent types of spider webs seen this late in the year is the sheet web, made by members of the Lynyphiidae family.

Several different web designs are found in this family including the bowl and doily, dome, and sheet. Tiny sheet web weavers spin small horizontal sheets of webbing and then hang upside-down underneath their web. Some species make two layers and hide between them for protection. When a small insect walks across the web, the spider bites through the silk, grabs its prey, pulls it through the web and eats (actually drinks) it.

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Spiderlings Dispersing

9-25 spiderlings dispersing 615Although many spider eggs hatch in the spring, there are some that hatch in the fall. Most spiderlings stay within the egg sac until they undergo their first molt – their small cast skins can be seen inside the old egg sac. After molting they emerge and cluster together, still living largely upon the remnants of yolk sac in their abdomens. In several days the spiderlings are ready to disperse, which is necessary to avoid competition for food and prevent cannibalism among the hungry siblings.

Some species, especially ground dwellers, disperse by walking, often over relatively short distances. Others, particularly foliage dwellers and many web builders, mainly disperse by ballooning. To balloon, spiderlings crawl to the top of a blade of grass, a twig or a branch, point their abdomens up in the air and release a strand of silk. Air currents catch the silk, often called gossamer, and lift the spider up and carry it off. Aerial dispersal may take a spiderling just a few feet away or much, much farther – spiderlings have been found as far as 990 miles from land. (Charles Darwin noted spiderlings landing on the rigging of the Beagle, 62 miles out to sea).