The herbivorous side of spiders
Spiders are famous for being voracious predators; indeed, some spiders may even eat bats. However, not all spiders are fully carnivore. In 1984 it was first suggested that pollen may have a role in the diet of some juvenile spiders and in 2009 one research showed that one particular spider species (Bagheera kiplingi; see picture below) mainly feeds on plant materials. Other observations of spiders eating plants or fungi are more scattered but a recent review identified a total of 95 records involving more than 60 spider species.
When wolves eat an herbivorous prey, they also feed on plant material present in their gut; this is a kind of "indirect" feeding on vegetables. However, every dog owner knows that, from time to time, dogs may eat some grass and wolves are known to do this too; this can be judged to be direct feeding on vegetables although, for dogs and wolves, it is usually a small part of their diet. So, clearly, being a predator and carnivore does not mean you can not eat vegetables. Spiders may also indirectly feed on plant material through feeding on herbivorous prey; however, many different spider species also directly feed on plants and fungi and, sometimes, the amount of vegetable food can not be considered just a small part of their diet. Bagheera kiplingi, the most extreme known case, can live almost exclusively feeding on plant material.
Spiders may feed on plant and fungi in different ways. They may be:
- leaf feeders (biting off or removing small leaf pieces or piercing leaves to extract plant sap),
- sugar feeders (feeding, for example, on nectar or on honeydew),
- pollen feeders (they may find pollen in their environment, on pollen-carrying insects, or on their webs since pollen is frequently trapped in spider webs),
- seed feeders (tiny airborne plant seeds are frequently trapped in spider webs), and
- spore feeders (airborne spores from different fungal species are also regularly trapped in spider webs).
It is not currently known the role of feeding on plant material on the "energy budget" of different spider species. However, this phenomenon has been largely underestimated. Pollen feeding by web-building spiders, for example, may be relatively common. More observations are needed.
All scientific information are from: Nyffeler, M., Olson, E., & Symondson, W. (2016). Plant-eating by spiders Journal of Arachnology, 44 (1), 15-27 DOI: 10.1636/P15-45.1
Picture is from