The male desert locust,
Schistocerca gregaria
, has two masses of thin glands, each mass containing 16 glands. The glands in each mass are arranged in a precise manner, which is a mirror image of the arrangement to be found in the other gland mass. They produce secretions which participate in the production of the spermatophore and most of its contents during mating. The fine structure of these glands is described in detail on the basis of an electron-microscope study of sectioned glands and their secretions. It is revealed that the characteristics of the glandular epithelia and their corresponding secretions lead to the division of the accessory glands into nine distinct types. This finding strengthens the recent division of the glands into nine types based on histological, histochemical, and phase-contrast features. One gland produces a proteinaceous, crystalline secretion (gland 1), three types of glands produce a minutely fibrous secretion (glands 2 and 4, and ‘homogeneous’ glands), three other gland types produce a globular secretion (glands 6, 11 and 12), and one gland type has a lipoid secretion (gland 3). Gland 16, the functional seminal vesicle, does not produce a recognizable secretion. The cytoplasmic organelles that are concerned in the secretory process, and the manner in which their development varies with each gland type, are discussed.