The typical hymenopteran has two pairs of membranous wings, the front and hind ones being coupled by a row of minute hooks on the leading edge of each hindwing. The latter is usually very much smaller than the forewing and not always easy to detect, even while the insects are at rest. Wing venation is often much reduced, producing a network of large and often rather square cells not seen in any other group of insects. The head is usually rather hard and extremely mobile, being attached to the thorax by a slender neck. Three ocelli are usually present in addition to the compound eyes.