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Thursday, May 28, 2009

Labyrinth Orbweaver

The tops of my shrubs along the public sidewalk are decorated with little agglomerations of elm seeds, elm leaves, rose geranium petals, and whatnot known as the retreats of labyrinth orbweavers, Metepeira labyrinthea. These spiders weave an orb web for catching prey, and a so-called irregular web (an unstructured mess of silk and detritus) behind and slightly above the orb web where she builds her retreat connected to the orb web by trap lines. The retreat is a tubular silk affair tilted down at about a 45 degree angle, shingled with bits of whatever is available and the right size. The retreat is enlarged over time as is the orb web repaired as needed; the spider spends the rest of her time hanging in the entrance waiting for prey and avoiding rain or the morning dew. The retreat shown here is about 1.5 inches long x 1/4 diameter at the opening and is built at the top of my rose geranium espalier about 4 feet above the ground.

These spiders are colonial, meaning they are not averse to living in close proximity to each other. I've got several; probably would have more except for the healthy population of other predators (birds, mantids, assassins, wasps, lizards) that keep most species in the garden from becoming dominant.

The female labyrinth spider produces several egg sacs, in a row like peas or beads, then camouflages them with plant matter in the same manner as the retreat. In fact, I thought this nest was a retreat until I took a closer look and saw the round silk-covered egg sac within. Tiny black spiderlings hatched out of here and dissipated in mid May.

A few days ago I checked on this spider, and found a bee hung in her orb web. There has been no sign of the spider in the retreat or nearby. Did she get mortally injured in the fight to subdue this honeybee?


michael said...

Fantastic set of photos. I have a Metepeira labyrinthea in my back yard I have been watching over the past month.(Martinez CA-Contra Costa County) Fasinating hideaway she makes....I have not seen an egg sack yet but now that I read your description, I will be on the look out.

vanessa cardui said...

I have great affection for these little spider-builders. Happy watching there in N. Cal.