Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Great Oak Beauty (Hypomecis roboraria) is a moth of the family Geometridae. The species can be found in Europe.The wingspan is 40 50 mm. The moths fly from May to August.The caterpillars feed on oak. A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth (about ten times the number of species of butterfly), with thousands of species yet to be described.