Male unknown in New Zealand and Europe, doubtful in America. Colour stated by Riley (Fifth Missouri Report, p. 95) as "translucent corneous-grey."
Habitat in New Zealand—On apple, pear, plum, peach, apricot, lilac, ash, thorn, sycamore, cotoneaster, and other plants, passim.
An introduced European species, known in America and elsewhere as the "oyster-shell bark-louse of the apple." It is the commonest, apparently, of the Diaspidinæ; and does great damage in orchards.
This species has been referred to by many writers under the specific name "conchiformis;" some authors include it under the genus Aspidiotus, others under Coccus, and one—Réaumur—under Chermes. In the Quarterly Journal of the Royal Microscopical Society, February, 1885, Mr. A. Michael refers to it as Coccus (Mytilaspis) pomicorticis.
The groups of spinnerets have been stated above to be "variable." The following table shows the numbers observed in specimens from different trees in New Zealand:—
| —— | Uppermost Groups. | Upper Side Groups. | Lower Side Groups. |
| Apple | 17 | 17 | 14 |
| Plum | 20 | 17 | 17 |
| Lilac | 17 | 19 | 16 |
| Ash | 10 | 12 | 9 |
| Cotoneaster | 7 | 15 | 10 |
A very minute white Acarid (mite) has been observed frequently under the puparia of this species, among the eggs. The eggs, in most cases so observed, were shrivelled and dead. Mr. A. Michael, in the paper above mentioned ("Notes on Tyroglyphidæ") refers to an Acarus found in America in 1873, also in puparia of M. pomorum, by Mr. Riley, and expresses doubts whether or not it fed upon the insect; yet he says, "A Tyroglyphus not ordinarily predatory might regard a Coccus as suitable for gastronomic purposes."
20. Mytilaspis pyriformis, Maskell.
N.Z. Trans., Vol. XI., 1878, p. 194; Vol. XIV., 1881, p. 215; Vol. XVII., 1884, p. 22.
([Plate V.], Fig. 6.)