It is the 'Rosemary beetle' there was an article on it in the RHS magazine this month.
It affects Lavender,Rosemary,Thyme & Sage
In midsummer the pest is present as non-feeding adults but in late summer they start feeding,mating and laying eggs.
Either remove them by hand or spray with sprays containing bifenthrin(Bug clear) on lavender and pyrethrum or rotenone on herbs.
Avoid spraying when plants are in flower to protect the bees.
the part in italics is courtesy of the RHS magazine 'The Gardener'