Fine structure and function of the prosomal glands of the two-spotted spider mite, Tetranychus urticae (Acari, Tetranychidae).

The prosomal glands of Tetranychus urticae (Acari, Tetranychidae) were examined light and electron microscopically. Five paired and one unpaired gland are found both in females and males. The silk spinning apparatus consists of paired silk glands which extend laterally on both sides of he esophagus into the pedipalps. There, they enter the terminal silk gland bag which opens into a silk bristle at the apex of hte pedipalps. The salivary secretions are formed in three paired glands which have an interconnecting duct, the podocephalic canal. The dorsal podocephalic glands may produce a serous secretion, the anterior podocephalic glands a mucous secretion, and the coxal organ may add a liquid, ion-rich secretion. These secretions pass the podocephalic canal and reach the mouth at the apex of the gnathosome. The function of the paired tracheal organs and the unpaired tracheal gland is still unclear. The tracheal gland may produce a secretion which facilitates the movement of the fused chelicerae and the stylets.