A balanced diet for spiders?

It's not just good for them, it's good for us:

Money spiders – or Linyphiidae - are a vital controller of pest numbers on farms because their prey includes aphids. However, aphids have poor nutritional value and are sometimes toxic, so the spiders need to balance their diet with other prey.

In a field experiment, the Cardiff team's analysis showed that the money spiders were eating large numbers of small insects called springtails or Collembola. Stomach contents showed that they were eating several different species of Collembola, but with strong preferences – DNA from a species, which was uncommon at the site where they were collected, proved to be present most frequently in the stomachs of the spiders.

"The DNA analysis enables us to identify precisely what the spiders have eaten," said Dr Symondson. "If we compare that with the prey populations in the field, we can see which prey the spiders prefer to eat when they have a choice."

"If we can encourage this prey insect in greater numbers, it should boost the population of spiders and therefore provide better control of aphids," said Dr Symondson.

In short, you might need more bugs before you can have fewer bugs. Or something like that.