Stuart produced a cocktail set with gruesome-looking spiders in 1935 - illustrated in McConnell, Miller's 20th Century Glass, p241. A single glass sold recently on e-bay for £33 (McConnell suggests £350 for the set). And they did produce enamelware in a similar shade of green - eg the flowered pot illustrated in this Cambridge Glass Fair feature:
http://www.cambridgeglassfair.com/exhibitions/pastexhibitions/2006-02-stuart.htm. Their chief designer Ludwig Kny came from a family of Czech glassmakers, which would account for the similarity to Bohemian enamelware.
But all the pieces I've seen have had "Stuart England" etched on the base. And your bugs seem a little more naturalistic and less cartoon-like than the Stuart spiders.
Stop press - just went to search for the spider glass on e-bay and discovered a cocktail shaker in the same pattern, but without the Stuart attribution, which went for only £10.50 - dammit: 160041380023. Note to self: must revise my search terms!