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05 January 1996
Vol 271, Issue 5245

About The Cover

Epitracheal gland (EG) of a Manduca sexta (tobacco hornworm) pharate pupa. The gland is composed of a large Inka cell (left, ~140 micrometers in diameter), which produces the ecdysis-triggering hormone, and two smaller glandular cells (right). Individual EGs are attached to the ventral side of the tracheal tube adjacent to each spiracle, comprising a peripheral, segmentally distributed endocrine system of 18 glands per animal. See 88 and the Perspective on 40. [Image: Duan itan]