Fig. 309.—Digestive canal of Sphinx ligustri: h, œsophagus; i, rudiment of the gizzard; k, “stomach”; q, its pyloric end; t, food reservoir; p, urinary tubes; l, ilium; m, cœcum of colon; n, rectum; v, vent.—After Newport.
In the mole-cricket the hinder part of the crop is armed within with hook-like bristles directed backwards so as not to prevent the energetic pressure of the food backwards into the proventriculus, and to obviate the possibility of a regurgitation. (Eberli.)
The fore-stomach or proventriculus.—This is especially well developed in the Dermaptera, in the Orthopterous families Locustidæ, Gryllidæ, and Mantidæ, while in the Thysanura (Lepisma) there is a spherical gizzard provided with six teeth. It also occurs in many wood-boring insects, and in most carnivorous insects, notably the Carabidæ, Dyticidæ, Scolytidæ, in the Mecoptera (scorpion-flies), in the fleas, and in many kinds of ants, as well as Cynips, Leucospis, and Xyphidria. It is very muscular, lined within with chitin, which is usually provided with numerous teeth arising from the folds. These folds begin in the œsophagus or crop, and suddenly end where the mesenteron (“chylific stomach”) begins. It has been compared with the gizzard of birds, and is usually called by German authors the chewing or masticating stomach. (Kaumagen.)
The proventriculus is best developed in the Gryllidæ (Acrida viridissima), where the six folds at the end of the crop close together to form a valve between the crop and proventriculus. “They are each armed with five very minute hooked teeth; and, continued into the gizzard, develop many more in their course through that organ. These first teeth are arranged around the entrance to the gizzard, and seem designed to retain the insufficiently comminuted food and to pass it on to that organ.
Fig. 310.—Anatomy of Danais archippus after removal of right half of the body. Lettering of the head: a, antenna; ph, pharynx; pl, labial palpi; r, proboscis; g, brain; usg, subœsophageal ganglion. Lettering of the thorax: I. II. III. thoracic segments; b1, b2, b3, the coxal joints of the three pairs of legs; bm, muscles of the wings; ac cephalic aorta with its swelling; œ, œsophagus; bg, thoracic ganglia of the ventral cord; sd, salivary glands of one side, those of the other side cut off near their entrance into the common salivary duct. Lettering of the abdomen: 1–9. abdominal segments; h, heart; sm, so-called sucking-stomach (food-reservoir); cm, chyle-stomach; ag, abdominal ganglia: ed, hind intestine with colon (c) and rectum (r); rm, urinary vessels; ov, ovarial tubes, those of the right side cut off; ove, terminal filaments of the ovaries; bc, bursa copulatrix; obc, its outer aperture; od, oviduct; vag, vagina; wo, its outer aperture; ad, glandular appendages of the vagina partly cut away; vk, connective canal between the vagina and bursa copulatrix with swelling (receptaculum seminis); an, anus.—After Burgess, from Lang.
Fig. 311.—Transverse section of the proventriculus of Gryllus cinereus: muc, muscular walls; r, horny ridge between the large teeth (sp).—After Minot.
Fig. 312.—Transverse section of the proventriculus of the cockroach.—After Miall and Denny.