The Entomological Society of America claims insects are "1.6 billion" times as numerous as humans. With just over 6 billion humans, that works out to about 10^19 insects.
That may sound like a lot, but there are many small life-forms that could be more numerous. For example, in soil the insects and mites (a type of arachnid, not an insect) all feed either directly or indirectly off various types of nematodes (a tiny worm, which also is not an insect). Nematodes are animals, and "often outnumber other animals" in many environments so they may be the most numerous animal.
That may sound like a lot, but there are many small life-forms that could be more numerous. For example, in soil the insects and mites (a type of arachnid, not an insect) all feed either directly or indirectly off various types of nematodes (a tiny worm, which also is not an insect). Nematodes are animals, and "often outnumber other animals" in many environments so they may be the most numerous animal.
