GIANT SPIDER INVASION IN THE GORGE!

Spike · Since 13 May 2007 1414 Posts Alameda Spelling Expert

I'm spreading FUD... Twisted Evil

What is the deal with all the massive cobwebs in just about every tree along I-84 between cascade locks and multnomah falls? It leaves the leaves dead underneath. I was trying to figure out if it was a spider or some disease cause it seems to be most common on the trees with the white bark, I think they are birch trees but can't be sure. Anyways, some insight would be nice.

Mark · Tue Aug 07, 07 8:15 pm

I think the trees you are seeing are Cotton woods. The webs are from an insect called Fall Webworm.
The fall webworm, Hyphantria cunea (Drury), is most often discovered when the unsightly, light gray, silken webs on the trees in late summer and early fall are observed. Webworms enclose leaves and small branches in their nests, unlike the tent caterpillars which make a smaller nest in the crotch of branches.

This pest is native to North America and is common from Canada into Mexico. It is one of the few American insect pests that has been introduced into Europe and Asia. Fall webworm larvae have been known to feed on over 85 species of trees in the United States.

The large silk webs enclosing tips of branches are sure signs of fall webworms. The caterpillars remain inside the webbing, and if food runs out new foliage is encased. The caterpillars are covered with long white to yellowish tan hairs. Two races of fall webworms occur in North America, the blackheaded and redheaded races. The blackheaded race has caterpillars which are light greenish-yellow to pale yellow with two rows of distinct black tubercles. The redheaded race is more tan in color with orange to reddish tubercles. The caterpillars make distinct jerking movements in unison if the nest is disturbed. The adults are about one inch long and range from pure white to white with a few black spots.

This pest overwinters in the pupal stage. Pupae are usually in the ground but can be located in old nest remains, under loose bark and in leaf litter. The adults emerge from late May into July. The eggs are usually deposited in a single (blackheaded race) or double (redheaded race) layer of several hundred eggs on the undersurface of leaves. The mass is lightly covered with scales from the female's abdomen. The eggs hatch in about a week and the small mass of caterpillars web over single leaves and feed by skeletonizing. As the caterpillars grow, they web over additional leaves and finally are able to eat the entire leaf. The larvae mature in about six weeks, at which time they drop to the ground to pupate.

Though the webs are very unsightly, damage to most trees is considered to be insignificant. However, in southern states where several generations of attack can severely defoliate trees, control measures are needed. This pest tends to go through periodic population explosions. Outbreaks every four to seven years may last for two to three years and then natural control agents greatly reduce the activity.

Mark · Tue Aug 07, 07 8:28 pm

Fall webworm

Spike · Since 13 May 2007 1414 Posts Alameda Spelling Expert

sweet, now I kow, thanks mark.

tinyE · Since 21 Jan 2006 2004 Posts not really an XTreme Poster

mark, please tell me you cut and pasted that out of an encyclopedia, and didn't know that.

also... does this appearance of webworms mean it is already fall? Sad

pdxmonkeyboy · Wed Aug 08, 07 10:17 am

in addition to the webworms, it is "spider season" in so much as during this time of the year many spider spin webs in order to catch the winds and migrate. Spiders and other web spinning insects can actually get carried by jet streams half way around the world! It's pretty trippy but spiders have been observed (dead of course) near the summit of mt. everest. After the st. helens explosion, some of the first insects found within the blast zone were spiders.

kind of trippy stuff, but if you are in the right place and the sun is blocked by a building ot some kind of rock formation, you can see thousands and thousands of webs flying through the air.

I witnessed such a thing at smith rocks year ago, right after reading about the spider flying phenom.

Yardsale · Since 29 Mar 2005 387 Posts Portlanastan Obsessed

Spike these webs are formed by the Giant Camel Spider also found in Iraq, Mark is just trying to put you at ease with that silly "web worm" story. Stay away from the trees cause although these are not venomous they can bite your head clean off....................the one on the bottom is eating the one on top by the way.......happy dreams! Shocked

Gman · Since 11 Feb 2006 4907 Posts Portland Unstrapped