The venom of the European Ant Monomorium is composed of five alkaloids: three 2.5 transdialkylpyrrolidines and two 2.5 transdialkylpyrrolines. The venom is synthesized by a glandular complex composed of a biramous external filamentous gland, and a single internal gland invaginated into the reservoir. External glands and the proximal two-thirds of the internal gland are composed of glandular units, with one glandular cell and one associated duct cell. Glandular cells contain numerous giant mitochondria, a well-developed smooth endoplasmic reticulum and enigmatic rod-shaped structures. The secretory product is electron-lucent. The distal third of the internal gland is composed of 38-48 large secretory cells issuing directly into the reservoir. Their secretory product presents the same characteristics as the venom accumulated in the reservoir (opacity, affinity to stains and osmium).