We call the larvae wireworms. Finally, one spring, they become adults. Their name comes from the clicking noise made when one is on its back and springs into the air to right itself. The adult click beetle, as well as the adult firefly, does not eat. Given that insects make up more than half of all the living things on earth, it seems a good thing that spiders, birds, mammals, and other insects include insects in their diet.
Insects are an excellent source of protein.
Many birds eat insects, focusing on what is most abundant at any particular time. They then supplement their diets with seeds or fruits when insects are less numerous. There are many species of birds that feed their young exclusively on insects, because the young need a high level of protein to develop. Another fortunate function of insects is pollination, which results in many of the fruits, vegetables, and seeds that we, and other animals, have come to enjoy. If you are interested in insects and spiders, some references are helpful.