There a number of techniques which are incorporated into this aspect of Art. There are also various apps and workshops that can be used to create the photomontage including Paint, Photoshop and other Digital imaging websites.
Insects made from old watches…Really cool. Where the bulbs & transistor/fuse type thingies come from? Doesn't really matter whether they do or don't come in watches. These are works of genius & art . in my not always so humble openguin.