Spiders have always been known to feed on insects, but zoologists from the University of Basel, the US, and the UK have now been able to show that their diet is more diverse than expected. Their findings show that spiders like to spice up their menu with the occasional vegetarian meal. The Journal of Arachnology has published the results.
Some spiders have been shown to enrich their diets by occasionally feasting on fish, frogs, or even bats. But the new study shows evidence of spiders eating plant food as well.
The researchers gathered and documented numerous examples from literature of spiders eating plant food. According to their systematic review, spiders from ten families have been reported feeding on a wide variety of different plant types such as trees, shrubs, weeds, grasses, ferns, or orchids. They also show a diverse taste when it comes to the type of plant food: nectar, plant sap, honeydew, leaf tissue, pollen, and seeds are all on the menu.
The most prominent group of spiders engaged in plant-eating are Salticidae, a diurnal spider family with characteristically large anterior median eyes. Salticidae were attributed with up to 60 percent of all plant-eating incidents documented in this study. As plant-dwelling, highly mobile foragers with an excellent capability to detect suitable plant food, these spiders seems to be predestined to include some plant food in their diets.
Spiders feeding on plants is global in its extent, as such behavior has been reported from all continents except Antarctica. However, it is documented more frequently from warmer areas. The researchers suggest that this might be due to the fact that a larger number of the reports relate to nectar consumption, which has its core distribution in warmer areas where plants secreting large amounts of nectar are widespread.
“The ability of spiders to derive nutrients from plants is broadening the food base of these animals,” said lead author Martin Nyffeler. “This might be a survival mechanism helping spiders to stay alive during periods when insects are scarce. In addition, diversifying their diet with plant[s] is advantageous from a nutritional point of view, since diet mixing is optimizing nutrient intake.”
However, the extent to which the different categories of plant food contribute to the spiders’ diet is still largely unexplored.
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