This group consists of the tumbling flower beetles, and are characterised by their wedge shaped body with along spike that protrudes from their abdomen. They get their name from the way they fall to the ground when the foliage they are on are disturbed.
To ID these I would recommend keying properly and the images on this page are merely to show examples of the group
Their wedge shaped dainty form is very similar to another group that is rarely encountered in moth traps: The Scraptiidae, although these are easilly separated by the lack of a 'spear' at the end of the abdomen
For a more indepth overview of the group I recommend Mark Telfers site