A bug party is the one theme where the real thing is free, already outside, and better than anything you could print.
One magnifying glass per child, a garden or a park, and a simple tally sheet of things to find — a worm, an ant, something with wings — needs no setup and holds attention for a genuinely long time, because it is real and slightly unpredictable.
Bundled sticks, pine cones and dry leaves stuffed into a small box or stacked bricks, made together during the party, is still standing in the garden months later. Most party crafts are binned within a week; this one is not.
If food and an outdoor bug hunt are happening on the same afternoon, keep the eating area separate from the hunting area. It solves itself and needs no more thought than that.
A tray of soil or a few branches brought indoors, with a couple of woodlice or a worm in a container to observe and return, still delivers the "real, not a toy" part that makes this theme work.
Look and catch gently, then release, works well for most bugs. Avoid anything that stings, and supervise closely with anything younger than about four.
Part of our guide to Birthday party for one obsession.