Quarterly Journal of Microscopical Science, Vol s2-80, 127-148, Copyright © 1937 by Company of Biologists

Memoirs: The Structure and Development of Wax Glands of Pseudococcus Maritimus (Homoptera, Coccidae)

¹ Department of Zoology, Columbia University

The females of Pseudococcus maritimus have three types of multicellular wax-glands, one with a triangular external pore, another opening through a long tube, and a third with a multilocular aperture. The first two are widely distributed on all surfaces of the adult. The third is restricted to the ventral surfaces of the last five segments. This multiloeular type is found only in the adult. The triangular glands are found at all stages and these structures progressively increase in number with each successive instar. The tubular type appears first in the second instar; the number is reduced in the third instar; and in the adult it is again increased to the largest number found at any stage.

The three glands are all modifications of one general plan of histological structure. The glandular elements are sub-epidermal cells arranged in a ring of peripheral cells surrounding a single central cell. There are three peripheral cells in the triangular gland and ten in each of the others. The peripheral cells are uninucleate and contain vacuoles of secretory material. The central cell of the tubular and triangular glands has a large and two small nuclei and contains a large reservoir, from which a chitinized duct system leads to the gland-pore. The central cell of the multilocular gland is small and relatively undifferentiated. The author favours the view of ulc that the wax is probably secreted by the peripheral cells, while the central cell secretes a substance that causes the wax filaments to adhere to form large cylinders.

The glands are developed by cell-multiplication from the epidermis at the time when it is freed from the cuticula at the beginning of ecdysis. After the initial period of cell-multiplication the first differentiation is the development of the external pore within the neck-cell. Later in the development of multilocular glands it is believed the glandular cells grow through the neck-cell to establish the functional relationship with the pore. It is suggested that this is analogous to the relationship between tormogen cell and trichogen cell in the development of a spine.