When it comes to beneficial insects in the garden, spiders receive little acknowledgement for their contributions. Perhaps it is because some leave nasty bites and thus scare us. Or perhaps it is because they perform the work of protecting our plants and crops quietly. In the shadows of the ever popular ladybug, our spider friends work tirelessly and without recognition. The real reason may be technical– spiders are not insects but rather arachnids. Humor aside, perhaps it is time to shine the spotlight on our eight-legged friendamies.
Here in the gardens, the tender plants are vulnerable to a number of pests that include woodlice, slugs, aphids, and cutworms/caterpillars (to name a few). The plants that make it past the woodlice and slug onslaught grow mature enough to face aphids and caterpillars. Between the two, caterpillars are quite obtrusive. When they are small, caterpillars are difficult to detect. By the time their presence is known, they often would have severely damaged the plant beyond repair. For many, the easiest solution is to spray plants down with pesticide.
Unbeknownst to the gardener, they may very well be committing friendly fire by taking out beneficial insects (and arachnids); like spiders. Who knew that spiders are beneficial? Probably not too many of us. I had a sense but certainly did not. That sense was felt earlier this year when growing Brussels sprouts plants. Out of the three plants one stayed healthy. The two that did not fair well was pulled so as to not harbor pests. The plants were observed for differences in order to note what fostered failure and what enabled success. What was noticed on the healthy plant was the presence of a yellow sac spider (cheiracanthium inclusum). While it was never spotted with a caterpillar, there was definitely a sense that that spidy was endowed with great responsibility.
A few days ago, the spidy sense was turned into confirmation after seeing a male Hentzia jumping spider (hentzia palmarum) carry around a young caterpillar presumable to snack on.
More information about garden spiders can be found at: http://web.pdx.edu/~smasta/MastaSpidersYard.html