Sheet Webs With a Funnel at One Side

Dew makes visible what is there all summer: a lawn can hold hundreds of sheet webs, each with a spider in a funnel at one edge.

The web

A flat, slightly dished horizontal sheet, usually between grass stems, in a shrub, or spanning a step or a wall corner.

At one side, a tube of silk leading back into cover. The spider sits in the mouth of that funnel with its legs on the sheet, feeling for vibration.

The sheet is not sticky. It works by tripping insects that walk or land on it, and the spider is fast enough to reach them before they recover.

The spider

Long-legged, brown, with dark longitudinal stripes on the cephalothorax and a pair of prominent spinnerets projecting from the rear of the abdomen.

Those visible spinnerets are the useful field mark for the family, and they are visible in a photograph of a spider seen from above.

They run remarkably quickly on a flat surface and stop abruptly.

Why the confusion with hobo spiders

Hobo spiders are in the same family and look similar, which is the whole source of the identification difficulty.

Separating them reliably requires examining genitalia under magnification, which is not a field exercise. That would matter more if hobo spiders were dangerous, and the evidence that they cause necrotic wounds has not held up — the account in the hobo spider myth.

So the practical answer is that a brown funnel-weaver in North America is harmless, whichever species it is.

Australian funnel-webs

An entirely separate family, found only in eastern Australia, genuinely dangerous, and unrelated to anything in North America or Europe.

The shared common name causes a recurring alarm that has no basis outside Australia, and it is worth naming explicitly because the search results for "funnel web spider" are dominated by a species most readers will never encounter.

In and around a house

Funnel weavers build in wall corners, window wells, under steps, in wood piles and along foundations.

They come indoors in autumn, chiefly males wandering to find mates — the seasonal pattern set out in spiders in autumn. Those are the fast brown spiders that cross a floor in September and cause most of the year's alarm.

Whether to do anything

They are harmless, they eat a substantial number of insects, and the webs disappear with the first hard frost.

Clearing webs from doorways and steps is reasonable. Treating a lawn because it has sheet webs in it means treating a lawn for having a functioning insect population, which is not a problem that needed solving.

Why dew reveals them

The sheets are there year-round in the growing season and are only visible when water droplets collect on the silk.

That produces the annual surprise of a lawn apparently covered in webs overnight. The webs were built over weeks; the dew arrived in one morning.

It is also why the phenomenon is associated with autumn, when cool nights and heavy dew coincide with the peak of the spiders' season.

Telling them from wolf spiders

Both are brown, fast and roughly the same size, and both turn up indoors in autumn.

Wolf spiders have no web at all and carry a distinctive eye arrangement with two large eyes facing forward. Funnel weavers have the projecting spinnerets and a web to go back to. The wolf spider comparison in wolf and nursery web spiders covers the group they are most often mixed up with.