The actual piercing organs are the mandibles, while the upper lip or labrum forms a sucking tube.
The labrum (fig,.
The maxillae are not piercing organs, and their function is to protect the mandibles and labrum and separate the hairs or feathers of the host.
Maxillary and labial palpi are also present, and the latter, together with the labrum or lower lip, form the rostrum.
a, Labium; b, maxilla; c, labrum; d, mandible.