https://blendermarket.com/products/insect-swarm---procedural-insect-systems

Whether it's for an old attic, a dark cave or just a colorful nature scene - Insect Swarm systems can help you breathe life into your scene in no time. You want crawling insects, flying swarms or even centipedes? These simulation node systems contain everything you need.  With just a few clicks, the insects move autonomously or guided over the surface you choose or fly through the air! You can also determine which objects the insects are attracted to and which they avoid. If you need them to go somewhere specific, you can use curves to tell them where to go! Each insect gets simulated individually!   Plus, with the purchase of this system, you'll get 21 different animated low-poly insects that have been optimized for the systems, so you can have thousands of insects running and flying around your scene at once!  That's not all! The systems as well as the insects are packed into one organized asset file, that lets you drag and drop whatever you need at any time into any project!