In the male cricket, the anal odoriferous glands are small lobes opening into a reservoir on each side of the rectum (Dufour). Homologous glands also occur in the Coleoptera (Fig. 302, l and 317, s).
Fig. 361.—Glands (g) of Lachnus; h, “honey” wart.—Gissler del.
Most Hemiptera or bugs send out a fœtid or nauseous odor due to a fluid secreted by a single or double yellow or red pear-shaped gland, situated in the middle of the mesothoracic segment, and opening between the hinder or third pair of coxæ. In Belostoma Leidy describes these glands as consisting of two rather long cœcal tubes situated in the metathorax, beneath the other viscera, extending backwards into the abdomen, and opening between the coxæ of the third pair of legs. Locy states that the smell arising from these glands is pleasant, resembling that of well ripened pears or bananas. Other bugs, moreover, emit an agreeable odor, that of Syromastes resembling that of a fine bergamot pear. (Siebold.) The fluid given out by the European fire-bug (Pyrrhocoris apterus) has a sweetish smell, like ether. In the nymph there are three pairs of dorsal glands, on abdominal segments 2–5, which are atrophied in the mature insect. In the bed-bug, the nymph has three odoriferous glands each with paired openings in the three basal abdominal segments respectively, and situated on the median dorsal line, being arranged transversely at the edge of the tergites; but after the last moult these are aborted, and replaced by the sternal metathoracic glands (Künckel). Gissler has detected a pair of glands in Lachnus strobi (Fig. 361).
Anal glands of beetles.—Certain beetles are endowed with eversible repugnatorial glands. Eleodes gigantea and E. dentipes of both sexes are said by Gissler to possess these glands. When teased “they stand on their anterior and middle legs, holding the abdomen high up and spurting the contents of the glands right and left.” The glands (Fig. 366, 1) are two reddish brown, somewhat bilobed sacs, and extend from the base of the last up to the middle of the 2d abdominal segment, with an average length of 6.5 mm. The liquid stains the human skin, has an acid reaction, with a peculiar, “intensely penetrant odor, causing the eye to lachrymate. It is soluble in water, alcohol, and ether. Boiled with concentrated sulphuric acid and alcohol an ethereal aromatic vapor is produced, indicating the presence of one or more organic acids, though neither formic or acetic acid could be detected.” Williston has observed the same habits in seven other species of Eleodes, all ejecting a pungent vile-smelling liquid, one species (E. longicollis) ejecting a stream of fluid from the anal gland, backwards sometimes to the distance of 10 cm. or more, and he regards these beetles as “the veritable skunks of their order.” Leidy briefly describes the odoriferous glands of Upis pennsylvanica.
The anal glands consist, according to Meckel and also Dufour, of two long, simple, flexuous cœca with reservoirs having two short excretory ducts situated near the anus (Siebold).
Glands like those of Eleodes found in Blaps mortisaga are described in detail by Gilson (Fig. 366, 2). They form two pouches or cuticular invaginations situated in the end of the abdomen on the sides of the end of the intestine and unite on the median line underneath the genital organs, forming a very short tube with a chitinous wall, continuous with the cuticle of the last abdominal segment. Into each pouch open a large number of fine slender lobules varying in shape, giving a villous aspect to the surface. These lobules are composed of as many as fifty unicellular glands, each of which is composed of four parts: (1) A radiated vesicle, (2) a central sac, giving rise (3) to a fine excretory tube, and (4) a sheath near the origin of the excretory tube. These are all modifications of the cytoplasm of the cell with its reticulum; the nucleus with its chromosomes is also present, but situated on one side of the central sac. The fine excretory tubules form a bundle passing down into the mouth of each lobule.
Similar glands, though usually smaller, which have not been carefully examined, occur in Carabus (Fig. 300, 3) and Cychrus, which eject from the vent a disagreeable fluid containing butyric acid (Pelouse). The bombardier beetle Brachinus, with its anal glands, ejects a jet of bluish vapor accompanied with a considerable explosion, which colors the human skin rust red; it is caustic, smells like nitrous acid, and turns blue paper red. Westwood states that individuals of a large South American Brachinus on being seized “immediately began to play off their artillery, burning and staining the flesh to such a degree that only a few specimens could be captured with the naked hand, leaving a mark which remained for a considerable time.” The fluid ejected by another species, in Tripoli, blackened the fingers of the collector. “It is neither alkaline nor acid, and it is soluble in water and in alcohol.” (Kirby and Spence, iv, p. 149.)
Species of other genera (Agonum, Pheropsophus, Galerita, Helluo, Paussus, Ozæna) are also bombardiers, though less decidedly so than Brachinus. A Paussid beetle (Cerapterus) ejects explosively a fluid containing free iodine (Loman), while Staphylinus, Stenus, Ocypus olens, Lacon, etc., have similar anal fœtid glands, the liquid being more or less corrosive. The secretion of Mormolyce phyllodes is so corrosive that it is said to paralyze the fingers for 24 hours after. (Cuénot.)
