with impervious wax, but rather add the porous capping, made of wax and pollen. The pupæ no less than the larvæ of some two-wing flies, which live in water, have long tubes which reach far out for the vivifying air, and are thus called rat-tailed. Even the pupæ of the mosquito, awaiting in its liquid home the glad time when it shall unfold its tiny wings and pipe its war-note, has a similar arrangement to secure the gaseous pabulum. The digestive apparatus of insects is very interesting, and, as in our own class of animals, varies very much in length and complexity, as the hosts of insects vary in their habits. As in mammals and birds, the length, with some striking exceptions, varies with the food. Carnivorous or flesh-eating insects have a short alimentary canal, while in those that feed on vegetable food it is much longer. [Illustration: Fig. 9. _Alimentary Canal._ _o_--Honey stomach. _b_--True stomach. _c_--Urinary tubes. _d_--Intestine. ] The mouth I have already described. Following this is the throat or pharynx, then the œsophagus or gullet, which may expand, as in the bee, to form a honey or sucking stomach (Fig. 9, _o_), may have an attached crop like the chicken, or may run as a uniform tube as in our bodies, to the true stomach (Fig. 9, _b_). Following this is the intestine--separated by some into an ileum and a rectum--which ends in a vent or anus. In the mouth are salivary glands, which in larvæ that form cocoons are the source of silk. In the glands this is a viscid fluid, but as it leaves the duct it changes instantly into the gossamer thread. Bees and wasps use this saliva in building their structures. With it and mud some wasps make mortar; with it and wood, others their paper cells with it and wax, the bee fashions the ribbons that are to form the beautiful comb. Lining the entire alimentary canal are mucous glands which secrete a viscid fluid that keeps the tube soft, and promotes the passage of food. The true stomach (Fig. 9, _b_) is very muscular, and often a gizzard, as in the crickets, where its interior is lined with teeth. The interior of the stomach is glandular, for secreting the gastric juice which is to liquify the food, that it may be absorbed, or pass through the walls of the canal into the blood. Attached to the lower portion of the stomach are numerous urinary tubes (Fig. 9, _c_) though Cuvier, and even Kirby, call these bile tubes. Siebold thinks some of the mucous glands secrete bile, and others act as a pancreas.