A weft feeder device for threads, in particular for weaving looms, of the type comprising a main body (1) within which there is housed an electric motor for the driving of a rotary shaft (2), the rotary shaft (2) driving into rotation, with its middle portion, a rotor (3), and a drum (T) rotatably mounted on the end portion of said rotary shaft (2) and kept fixed by magnetic means (6, 7), and wherein there are furthermore provided pairs of optical emitting/receiving sensors (E, R) are respectively arranged on the drum (T) and on an extension of the main body (I) of the weft feeder device which extends laterally to the lateral surface of the drum (T), said pairs of sensors (E, R) being apt to detect the presence/absence of a thread passing therebetween. The outer surface of said drum (T) consists of multiple independent sectors (4), and said emitting sensors (E) and the relative feeding and control circuit are embedded in the thickness of one (4s) of said sectors (4), arranged opposite said extension (10) of the main body (1) of the weft feeder device.