Hypodermis

noun

1. An epidermal layer of cells that secretes an overlying chitinous cuticle, as in arthropods.
2. A layer of cells lying immediately below the epidermis.
3. A subcutaneous layer of loose connective tissue containing a varying number of fat cells.
4. In annelids, as the earthworm, a thick layer, below the cuticula, of reticulated or nucleated tissue, in the meshes of which is a copious transparent gelatinous substance. It is considered by some as probably representing both the dermis and the epidermis of other animals.
5. In entomology, a soft cellular substance or tissue lining the abdominal wall of an insect, within the chitinous investment.