siphonet

from The Century Dictionary.

• noun In entomology, one of the two tubes on the upper surface of the abdomen of an aphis from which honeydew exudes; a honey-tube. Also called siphunculus.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) One of the two dorsal tubular organs on the hinder part of the abdomen of aphids. They give exit to the honeydew. See Illust. under aphis.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun zoology One of the two dorsal tubular organs on the rear part of the abdomen of aphids, which secrete honeydew.