Although spiders are not many people’s favorite animals, they are very important land carnivores that shape the structure of ecological communities and control the populations of their prey species. Some spider species, such as the South American “banana spiders” or “wandering spiders” (genus Phoneutria), are also of medical importance due to their strong poison.
Spider diets are derived primarily from field and laboratory observations, which may be biased and likely underestimate the number of species ingested. Spiders also externally digest their prey before ingestion, making it difficult to identify their prey.
With more advanced molecular techniques and ever-growing DNA databases, it is now possible to create molecular intestinal contents, that is, to sequence the DNA present in the intestines of the spiders and compare them with existing sequences in databases, which enables a more precise identification of species. This method is known as DNA meta-barcoding.
Researchers from the Universidad del Tolima and the Universidad de Ibagué in Colombia were the first to use DNA metabarcoding to analyze the diet of a wandering spider, Phoneutria boliviensis (disclosure: I, the author, worked on this project). We sequenced the intestines of 57 spiders and identified 96 types of prey from 10 orders, mainly flies, beetles, butterflies, moths, grasshoppers, grasshoppers and crickets. We also found the DNA of a species of lizard and snake among the prey species eaten by females.
In this study, females had fewer prey numbers than males, although the opposite was expected since females of these species are generally larger. However, these results indicate that the two sexes have different predatory strategies. The 57 spiders analyzed belong to three different populations in Colombia, and the prey composition of the individual populations also differed, which suggests that the three locations show small differences in the availability of prey.
This study confirms that migratory spiders feed on a greater diversity of species than previously reported, further confirming their generalist nature and flexible diet.