Capitate

1913 Henry Gray: Anatomy Descriptive and Applied The capitate bone is the largest of the carpal bones, and occupies the centre of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the navicular and lunate; a constricted portion or neck; and below this, the body. The superior surface is round, smooth, and articulates with the lunate.

1884 A. de Bary Comparative Anatomy of the Vegetative Organs of the Phanerogams and Ferns. Oxford University Press Capitate hairs occur on most leaf-forming plants, especially Dicotyledons and Ferns, as a rule in company with non-glandular hairs. It is true they are absent from many large groups... To this category belong in the first place the great majority of the universally distributed glandular hairs ... Meanwhile we need only remark here, that the glandular hairs are characterised by no special form, but rather by definite properties of the cell walls; therefore the terms capitate and glandular hair are not equivalent. In the case of many capitate hairs, it is as yet uncertain whether they possess the characteristic properties of glandular hairs...

Capitate antennae are thin through most of the structure, then abruptly widen, so it looks like the head of a pin sitting on the end of the antennae. This antennal shape is commonly found in butterflies.