I have just published keys to the British species of Megalopodidae and Scraptiidae (beetles), which can be found here -
The Scraptiidae beetles are found as adults on the blossom of spring-flowering shrubs, particularly hawthorn. Males are relatively easy to identify as they have appendages under the abdomen which are characteristic for different species. The most recent beetle checklist has fourteen species listed, but another is listed on the NBN distribution maps. This is all mentioned in the key.
The three species of Megalopodidae, all in genus Zeugophora are associated with poplars. One of them is restricted to the Scottish Highlands while the other two have a more general distribution in Britain.
As always if you find the keys useful, please tell me. If you find some things are difficult to follow or are plain inaccurate, please let me know and I'll correct them. It is my aim to have a resource that will be of use to entomologists.