I stumbled upon the following paragraph on the Wiki page about Argiope bruennichi:
When a prey item is first caught in the web, Argiope bruennichi will quickly immobilise its prey by wrapping it in silk. The prey is then bitten and then injected with a paralysing venom and a protein-dissolving enzyme.
On hindsight, it seems a bit redundant to do both those things. If prey is caught in the web, which is rather sticky and therefore restricts its movement, isn't it possible for the spider to go right ahead and inject venom?
Or on the other hand, if it wraps and immobilises the prey in silk, wouldn't it be more logical to then leave it to die, from some sort of evolutionary standpoint of wanting to saving energy and resources?