Sac. The cottony, bag-like covering or nest produced by the spinnerets and concealing the insect in many of the Coccidinæ and some Lecanidinæ. ([Plate XV], Fig. 1, c; Fig. 2, b.)
Scale. The shield or puparium of the Diaspidinæ. The word is commonly used to designate the outward appearance of insects of the whole family, which are indiscriminately called "scale-insects," although many of them form no shield whatever.
Secretion may be of various kinds. It is matter produced by internal organs, and expelled through the "spinnerets." In the Diaspidinæ the secreted portion of the puparium (that is, all except the pellicles) is made up of fine, closely-woven fibres, forming the "scale." In the Lecanidinæ it probably exudes originally as fine fibres, but these become agglomerated in some cases in a waxy or horny mass, or in others are loosely collected as cotton. In the Coccidinæ the secretion is usually cottony, or powdery like meal. Cœlostoma secretes all three—wax, cotton, and meal. In some instances, as in Carteria lacca, of Africa, the wax, called "shellac," is abundant enough to be commercially valuable; or, as in the Chinese Ericerus Pe-la it can be used for making candles.
Seta. A bristle—a long stiff hair.
Setose. Bearing a few bristles.
Spinnerets. Organs observed in various parts of the body, producing the waxy, cottony, or mealy matter. They consist of cylindrical internal tubes, sometimes ending on the skin, sometimes protruding outside it in the form of tubes, spines, or conical hairs. In the former case the orifices show them to be in some instances simple, and in others compound tubes.[B] In the Diaspidinæ, besides being scattered over the body, the spinnerets are arranged in groups on the last abdominal segment, and these groups afford excellent characters for specific distinctions. ([Plate I], Fig. 4, for types of various spinnerets; [Plate III], groups of spinnerets of Diaspidinæ.)
[B] Minute anatomical details are unsuitable for this work. The student may consult Targioni-Tozzetti, "Studie sulle Cocciniglie," cap. ii., p. 26.
Spiracles. "Breathing organs:" the orifices in the body of the tracheæ or tubes conveying air to the blood. In the Lecanidinæ they are usually four; simple circles, near the edge of the body, and with a few strong spiny hairs near them. In the Coccidinæ they are often numerous. ([Plate II], Fig. 4; [Plate XX], n.)
Spiracular spines. Spiny hairs, usually three in number, of which one is rather long, close to the spiracles, in the Lecanidinæ.