Yellow Garden Spider

Fall is peak spider season on PEI, and the most commonly-reported of our nearly 200 different species is the lovely Yellow Garden Spider (Argiope aurantia).

If you are among the 6% of the population that experiences arachnophobia – fear of spiders – you may not be happy with either today’s photo or my reference to just how many species the Island has. And, if that’s the case, you really won’t like me mentioning that one UK researcher estimated that there are as many as two million spiders per acre in some grassy habitats (a more recent report reduced this to a mere 600,000 per acre).

While all this spider biomass may be a nightmare for some, arachnids (including Yellow Garden Spiders) provide a valuable service, feeding on insects that would otherwise be pests of houses, gardens, agricultural crops, and our outdoor activities. Spiders are also useful, high-protein food sources for insect-eating migratory songbirds, as well as for overwintering birds, amphibians, reptiles, and mammals.

Yellow Garden Spiders are common in open areas and grassy fields across PEI, and you almost certainly have some around your yard. If you haven’t seen this species, you may have noticed its web, identifiable by the zigzag pattern down the middle. That middle strip is called the ‘stabilimentum’, and there are a few theories about its purpose.

While there’s debate about its exact role, we do know that the stabilimentum does not add structural stability to the web. The most common theory is that it serves as a warning to birds and mammals (including us!) to avoid the web; we’re too large for Yellow Garden Spiders to eat, and if we tear the web, the spider will need to expend energy rebuilding it.

Stabilimenta reflect UV light, and a second theory is that this helps attract insects that can see those shorter wavelengths. Yellow Garden Spiders align themselves with the stabilimentum while awaiting insects, and it’s also been suggested that it may help disguise the predator as it awaits prey.

Regardless of purpose, intricate webs and the Yellow Garden Spiders who build them are important parts of PEI Untamed!