LITERATURE ON THE EXCRETORY (URINARY) ORGANS
Malpighi, M. Dissertatio epistolica de Bombyce, Societati regiæ Londini ad scientiam naturalem promovendam institutæ dicata. (Londini, 1669, 12 Pls.)
Herold, M. J. D. Entwicklungeschichte der Schmetterlinge. 1815.
Rengger, J. R. Physiologische Untersuchungen über den tierischen Haushalt der Insekten. Tübingen, 1817, pp. 82.
Wurzer. Chemische Untersuchungen des Stoffes in den Gallgefässen von Bombyx mori. (Meckel’s Archiv f. Physiol., iv, 1818, pp. 213–215.)
Gaede, H. M. Physiologische Bemerkungen über die sogenannten Gallgefässe der Insekten. (Nova Acta Acad. Caes. Leopold.-Carolin., 1821, x, Pars II, pp. 186–196.)
Meckel, J. F. Ueber die Gallen- und Harnorgane der Insekten. (Meckel’s Archiv, i, 1826, pp. 21–36.)
Audouin, J. V. Calculs trouvés dans les canaux biliaires d’un cerf volant. (Ann. sc. nat., 2 Sér., 1836, v, pp. 129–137.)
Frey und Leuckart. Anatomie und Physiologie der Wirbellosen. 1843.
Dufour, L. Mémoire sur les vaisseaux biliaires ou le foie des Insectes. (Ann. sc. nat., 1848, Sér. 2, xix, pp. 145–182, 4 Pls.)
Karsten, H. Harnorgane von Brachinus complanatus. (Müller’s Archiv f. Anat. und Physiol., 1848, pp. 367–374.)
Fabre, J. L. Étude sur l’instinct et les metamorphoses des Sphégiens. (Ann. d. sc. nat., 4 Sér., 1856, vi, pp. 137–189.)
—— Étude sur le rôle du tissu adipeux dans la sécrétion urinaire chez les Insectes. (Ibid., 4 Sér., xix, pp. 351–382.)
Schlossberger, J. E. Untersuchungen über das chemische Verhalten der Krystalle in den Malpighischen Gefässen der Raupen. (Archiv f. Anat. und Physiol., 1857, pp. 61–62.)
Leydig, F. Lehrbuch der Histiologie. 1857.
Sirodot, S. Recherches sur les sécrétions chez les Insectes. (Ann. sc. nat., 4 Sér., Zool., 1858, x, pp. 141–189, 251–334, 12 Pls.)
Kölliker, A. Zur feineren Anatomie der Insekten (Ueber die Harnorgane, u.s.w.) (Verhandl. d. Physikal.-medizin. Gesellsch. in Würzburg, viii, 1858, pp. 225–235.)
Schindler, E. Beitrage zur Kenntnis der Malpighischen Gefässe der Insekten. 3 Taf. (Zeitschr. f. wiss. Zool., xxx, 1878, pp. 587–660.)
Chatin, G. Note sur la structure du noyau dans les cellules marginales des tubes de Malpighi chez les Insectes et les Myriapodes. (Ann. d. sc. nat., 6 Sér., xiv., 1882, pp. 7, 1 Pl.)
Witlaczil, E. Zur Anatomie der Aphiden. (Arbeiten a. d. Zool. Instit. d. Univers. Wien., iv, 1882, pp. 397–441, 3 Taf.)
Cholodkowsky, N. Sur les vaisseaux de Malpighi chez les Lépidoptères. (Compt. rend. Acad. d. Sc., Paris, xcix, 1884, pp. 631–633.)
—— Sur la morphologie de l’appareil urinaire des Lépidoptères. (Archives de Biologie, 1887, vi, pp. 497–514, 1 Pl.)
Loman, J. C. C. Ueber die morphologische Bedeutung der sogenannten Malpighischen Gefässe der echten Spinnen. (Tijdschr. Nederl. Dierk. Ver. (2) Deel 1, 1887, pp. 109–113, 4 Fig.)
Marchal, P. Contribution à l’étude de la désassimilation de l’azote. L’acide urique et la fonction rénale chez les Invertébrés. (Mém. Soc. Zool. de France, 1889, iii, pp. 42–57.)
Kowalevsky, A. O. Ein Beitrag zur Kenntnis der Exkretionsorgane. (Biol. Centralbl., ix, 1889–90, pp. 33–47, 65–76, 127–128.)
—— Sur les organes excréteurs chez les arthropodes terrestres. (Congrès international de Zool., 2me Session à Moscou, 1892, Pt. I, pp. 186–235, 4 Pls.)
Griffiths, A. B. On the Malpighian tubules of Libellula depressa. (Proc. Roy. Soc., Edinburgh, 1889, xv, pp. 401–403, Figs.)
Grandis, V. Sulle modificazioni degli epitelii ghiandolari durante la secrezione. (Atti Accad. Torino, 1890, xxv, pp. 765–789, 1 Pl.; Archiv Ital. Biol., 1890, xiv, pp. 160–182, 1 Pl.)
Koulaguine, N. Notice pour servire à l’histoire du développement des hyménoptères parasites. (Congrès internat. de Zool., 2me Session à Moscou, 1892, Pt. I, pp. 253–277.)
Sograff, Nicolas. Note sur l’origine et les parentés des Arthropodes, principalement des Arthropodes trachéates. (Congrès internat. de Zool., 2me Session à Moscou, 1892, Pt. I, pp. 278–302.)
Giard, Alfred. (Note on the urinary tubes of larval Cecidomyia. Annals Ent. Soc., France, lxii, 1893, pp. lxxx-lxxxiv, 1 Fig.)
Wheeler, William M. The primitive number of Malpighian vessels in insects. (Psyche, vi, May-December, 1893, Parts 1–6, pp. 457–460, 485–486, 497–498, 509–510, 539–541, 545–547, 561–564.)
Metalnikoff, C. K. Organes excréteurs des insectes. (Bull. Acad. imp. Sci. St. Pétersbourg, 1896, iv, pp. 57–72, in Russian, 1 Pl.)
See also the works of Straus-Dürckheim, Will (Müller’s Archiv. 1848, p. 502), Brugnatelli, Leidy, Dufour, Ramdohr, Basch, Davy, Grassi, Minot, Berlese, Adlerz, Marchal (Bull. Ent. Soc. France, 1896, p. 257); Bordas (Appareil glandulaire des Hyménoptères, 1894), also C. R. Acad. Sc. Paris, 1897.
e. Poison-glands
Poison-glands are mainly confined to the stinging Hymenoptera, i.e. certain ants, and the wasps and bees, but also occur in the mosquito, while many, if not most bugs, seem to instil a drop of poison into the punctured wounds they make.
In the honey and other bees the poison apparatus consists of two poison-glands whose secretion passes by a single more or less convoluted efferential duct into the large poison-sac, and thence by the excretory duct, which is enlarged at the base of the sting (Figs. 194, 195), out through the sting by the same passage as the eggs. According to Carlet, the poison apparatus of bees consists of two kinds of glandular organs, of which one kind secretes a feebly alkaline fluid, the other an acid product. The poison is only effective when both fluids are mixed. The resultant venom is always acid. The action of this venom upon some animals, as rabbits, frogs, and certain beetles, is slight; but the domestic fly and the flesh-fly are immediately killed by it. The inoculation of a fly with the secretion of one of the glands does not produce death until after a considerable time, but death follows very quickly if the same fly is subjected to a second inoculation, this time with the secretion of the other gland. The alkaline glands are in bees and all poisonous Hymenoptera strongly developed, but become vestigial in those forms which sting their prey to serve as food for their larvæ. The poison which the solitary sand and wood wasps and Pompilidæ inject into their victims only paralyzes them.
Fig. 348.—The poison apparatus of Ichneumon: T, sting; GA acid gland; TG, R′, its tubes opening into the common poison-sac or reservoir; ce, its efferent canal; Ga, the tubular alkaline gland; R, the glandular end; a, the reservoir; ce, its duct; Gac, the accessory gland—After Bordas.
Fig. 349.—Cephalic gland of Belostoma.
Bordas has found both the alkaline gland (gland of Dufour) and the acid gland to occur in a hundred species of Hymenoptera, including not only Aculeata, but also Ichneumonidæ (Fig. 348), Tenthredinidæ, and they may be safely said to be of general occurrence. The acid gland consists of three parts, the glandular portion, the reservoir for the poison, and the secretory canal. The alkaline gland is an irregular tube, with a striated surface and without a reservoir. In most Hymenoptera there is still a third gland, which is unpaired, granular, rectangular or lanceolate, with a short filamentous duct which opens beside the orifice of the alkaline glands.
The poison in ants, wasps, and bees consists of two substances, i.e. formic acid and a whitish, fatty, bitter residue in the secretion of the glands; the corroding active formic acid is the essential part of the poison. (Will.)
In Melipona the sting and poison-glands are aborted; in certain ants (Formica, Lasius, etc.) the sting is wanting, but the poison-sac is extraordinarily large.
Bordas finds in various species of Ichneumon three kinds of glands opening into the base of the sting. The first two correspond to the acid (Fig. 348, G.A) and alkaline (G.A) glands of bees and wasps (Vespidæ, etc.), and the third (G.ac) is situated between the two lateral muscular bundles which attach the base of the sting to the last abdominal segment. The poison-reservoir (Fig. 348, V) is recognized by its yellow color and diaphanous and striated appearance. It is situated on the left of the hind-intestine, a little in front of the rectum. The tubular gland (Ga) or alkaline gland of aculeate Hymenoptera is remarkably large; it is situated on the left side of the body. The accessory gland (G.A) is elongated, triangular, flat, its duct opening at the base of the alkaline gland; it is formed of small spherical cells. Bordas has met with well-developed poison-glands in forty species belonging to the Terebrantia, including that of Tenthredo, Emphytus, as well as various genera of Ichneumonidæ, but in all these species the accessory gland was wanting.
Fig. 350.—View from above of the cephalic gland of Belostoma, × 20.—This and Fig. 349 after Locy.
Under the name of cephalic glands (Fig. 349), Locy describes a pair of glands in the head of Nepidæ. The epithelial or secreting cells are 8–sided (Fig. 350). “When these insects are irritated,” he says, “a secretion is freely thrown out around the base of the beak, which produces death very quickly when introduced on a needle point into the body of an insect.” He infers that the cephalic glands may be the source of this poisonous secretion. The poisonous salivary fluid of the larva of Dyticus is referred to on p. 324.
That the mosquito injects poison into the wound it makes has been proved by Macloskie, who discovering fine droplets of a yellow oily-looking fluid escaping from the end of the hypopharynx, afterwards detected the poison-glands. It appears that the two salivary glands are subdivided, each into three lobes, the middle of which (Fig. 351, pg) differs from the others in having evenly granulated contents and staining more deeply than the others. Having examined the preparations, we agree with the discoverer that these lobes secrete the poison. The poison is diluted by the secretion of the salivary lobes, and the two efferent ducts, one from each set of glands, “carry forward and commingle the venomo-salivary products in the main duct; and the stream is then carried by the main duct to the reservoir at the base of the hypopharynx.”
Fig. 351.—A, median section of head, showing (du) the venomo-salivary duct, with its insertion in (hy) the hypopharynx; cb, brain; below is the pharyngeal pump, leading from (œ) the œsophagus; lre, base of labrum-epipharynx; m, muscle; n, commissure (other parts removed). B, the venomo-salivary duct, showing its bifurcation, and the three glands on one of its branches; pg, poison gland; sg, the upper of the two salivary glands. C, the bifurcation of the duct, with its nucleated hypodermis.—After Macloskie.
f. Adhesive or cement-glands
Dewitz has discovered in ants and bees, in close connection with the poison-glands, and like them discharging their secretion through the sting, cement-glands. They arise by budding at the base of the poison-glands.
The two glands in these Hymenoptera correspond to the tubular glands of the Orthoptera, which open at the base of the inner sheath of the ovipositor (Fig. 299, sb), so that the secretion flows out through it as the poison of bees, etc., out of the sting. The use of the secretion of these glands is either to glue the eggs together, or to afford material for the egg-case of cockroaches and Mantidæ and the gummy egg-case of the locusts, etc. The contents of the cement-glands serves for the fixture of the eggs after deposition. In the stinging Hymenoptera one of the cement-glands is an accessory gland; the other becomes the poison-sac. The cement-glands are in the Hemiptera only short blind sacs, in the Lepidoptera and Diptera long convoluted tubes, tubular and branched in the Coleoptera, or richly branched in the Ichneumonidæ and Tenthredinidæ. In the cockroach there are two cement-glands, but the right one is probably of no functional importance. The left one is filled with a milky substance, containing many crystals and a coagulable fluid, out of which the egg-capsule (oötheca) is formed. (Miall and Denny.) In the locusts the sebific or cement-gland (Fig. 298, sb) secretes a copious supply of a sticky fluid, which is poured out as the eggs pass out of the oviduct and agglutinates the eggs into a mass, forming a thin coating around each egg, which from the mutual pressure of the eggs causes the tough coating to be pitted hexagonally. In other insects also (Trichoptera, Chrysopidæ, Lepidoptera, etc.) there are similar secretions for the protection or fastening of the eggs when laid.[[57]] The Trichoptera lay their eggs either in or on the surface of the water in bunches or in strings or in annular gelatinous masses on stones or on plants. This jelly-like substance is secreted by two highly developed paired anal glands. (Weltner, in Kolbe, p. 621.) Also in certain dragon-flies (Libellula, Diplax, and Epitheca) the eggs are laid in jelly-like masses.
With a similar secretion, spun from the end of the abdomen, the Psocidæ cover their little bunches of eggs laid on the under side of leaves; and the silk thread forming the egg-sac of the great water-beetle (Hydrophilus) is secreted from such anal glands.
g. The wax-glands
Besides the honey-bee, which secretes wax in little scales on the under side of the abdomen, the bodies of many other insects, such as the plant and bark lice, as well as the Psyllidæ, Cicadidæ (especially Flata and Lystra), are covered with a waxy powder, or as in Chermes, Schizoneura, Flata, etc., with wool-like filaments of wax.
Fig. 352.—Under side of worker honey-bee, carrying wax scales, × 3.—After Cheshire.
Fig. 353.—Nymph of Lachnus, showing position of wax-glands.—Gissler del.
The wax is secreted by minute unicellular dermal glands, which in the lower insects (Hemiptera) are distributed nearly all over the body, but in the bees are restricted either to the under (Apis, Fig. 352) or upper side (Trigona) of the end of the abdomen.
The wax-glands of Pemphigus, Chermes, etc., lie under the little warts, seen in Lachnus strobi, the white-pine aphis, to be distributed in transverse lines across the back and sides of the abdominal segments (Fig. 353). These warts are surrounded by a chitinous ring, and divided into delicately marked areas. Through the delicate numerous pits in the chitinous membrane of these areas the little waxen threads project, since under each area ends a duct leading from a large glandular cell, which is a specially modified hypodermis cell (Claus). The wax threads are hollow, and all those arising from a single glued cell form a bundle, whose threads separate from each other and form a white woolly down or bloom covering the body. Witlaczil also shows that gall-forming Aphids secrete a wax-like substance, which, during the movements of the insects in the gall, is rubbed off, becoming a watery layer mixed with the fluid excrement, which forms a spherical impervious layer lining the gall, and thus rendering possible the mode of life of the gall-lice.
In the Psyllidæ Witlaczil has discovered wax-glands which also secrete slender waxen threads. They are situated in groups of two or three at the end of the abdomen near the anus, and arise from hypodermis cells. The wax threads surround the liquid excrement as it passes out of the vent, covering it with a continuous layer of wax. The excrement accordingly is discharged very slowly and gradually, in sausage-shaped masses slightly strung together and rolled into close spirals. The body becomes unavoidably smeared with the sticky excrement, since it is not entirely covered by the waxy layer. Moreover, in the larvæ of many Psyllidæ waxen threads are formed on the upper side of the abdomen; they are for the most part tightly curled or frizzly, like wool, and form, though partly torn, a waxen coat, chiefly on the side and back of the thorax and abdomen. The insects appear therefore as if covered with dust. The mature animals of many species are also covered with a waxen down. The wax threads rapidly dissolve and disappear in alcohol. From a wax-like substance more or less easily dissolved in alcohol arise peculiar hair-like structures which, in the larvæ of Psyllidæ, are situated on the side and end of the body and also on the rudiments of the wings. They are readily distinguished from ordinary hairs, as they arise from glandular cells, and are of very different lengths, more or less like bristles, but hollow, and very brittle. They are leaf-like in the first nymphal stages of Trioza rhamni, but in following stages become narrow and form a row around the entire periphery of the body.
The waxen dorsal shield which protects the body of bark-lice (Coccidæ) is a similar product.
Fig. 354.—Young nymph and developing scale of Aspidiotus perniciosus: a, ventral view of nymph, showing sucking beak with setæ separated, with enlarged tarsal claw at right; b, dorsal view of same, somewhat contracted, with the first waxy filaments appearing; c, dorsal and lateral views of same, still more contracted, illustrating further development of wax secretion; d, later stage of same, dorsal and lateral views, showing matting of wax secretions and first form of young scale; all greatly enlarged.—After Howard and Marlatt, Bull. 3, N. S., Div. Ent., U. S. Dept. of Agr.
Witlaczil has described the way it is formed in Aspidiotus and Leucaspis. The freshly hatched nymph shows no signs of a waxy secretion. But eventually waxen threads arise first on the hinder and anterior end of the body, and then over the whole surface. These threads interlace into a sort of felting and thus form the shield, which is usually much larger than the body and lies closely upon it. The shield is formed after the first moult. It is noteworthy that these threads are matted together to form as thick a tissue as that of the shield itself. The shield is whitish or gray and rather thin. On the thinnest part of the edge the single threads may be drawn out. The growth of the shield advances with the increase in size of the nymph around the entire edge, but is greatest behind. The first two larval skins are retained on the back under the shield. Also a very thin waxen pellicle remains on the resting place of the insect when it is raised. The wax-glands open in the pitted fields, and appear as clear brownish cells which are distinguished from the ordinary hypodermis cells by their greater size. (Witlaczil. Compare also Fig. 354.)
Fig. 355.—Wax disks of social bees: a, Apis mellifica, worker; b, do., queen; c, Melipona, worker; d, Bombus, worker.—From Insect Life, U. S. Dept. Agr.
The wax-glands in the honey-bee are scale-shaped organs situated on the under side of the four last abdominal segments (Fig. 355). These secrete the wax, which appears as whitish scales, and secretion is only possible when the bees have sufficient honey and pollen. The wax is secreted by the hypodermal cells rather than by glands within the abdominal cavity; the wax traverses the cuticular layer, and accumulates on its outer surface (Carlet). According to Fritz Müller, in the stingless bees (Trigona) which he observed, the wax-glands are situated on the back of the abdomen, but Ihering states that in many species of Trigona and Melipona there are also slightly developed wax-organs on the ventral side.
It has been found that certain caterpillars secrete wax. Thus the cells of the Tortrix of the fir (Retinia resinella) formed of resin are lined with wax, as on dissolving away the resin with alcohol, Dr. Knaggs found a slight film of wax; also a secretion of wax has been detected in the larva of a butterfly (Parnassius apollo). The bodies of certain saw-fly larvæ are covered with a white powdery secretion, while the remarkable larva of a Selandria is clothed with snow-white, long, flocculent, waxy masses, nearly concealing the body (Fig. 356).
h. “Honey-dew” or wax-glands of Aphids
The so-called “honey-dew” of Aphids which oozes from two wart-like tubercles or tubes situated near the end of the body, is secreted by hypodermal unicellular glands which open into a modification of a pore-canal, the tube itself being an outgrowth of the cuticula.
Witlaczil states that both in the “honey” tubes and in the body beneath, the sugary matter exists in cells of the connective tissue in the form of granules. “These large ‘sugar-cells’ in contact with the air undergo destruction, while the sugar crystallizes into needles, and thus each cell is transformed into a radiated crystalline mass.”
“A muscle extends from a horseshoe-shaped place (a valve?) in the middle of the flat terminal plate of the honey tube, through this and down through the abdomen to the ventral surface. By this muscle the honey tube is at times erected, and we then find, as also when we lightly press the body of the insect, lumps of crystallized sugar which have been expressed through the tips of the honey tubes.” (Zool. Anzeiger, 1882, p. 241.)
Fig. 356.—Wax-secreting larva of a saw-fly.
Fig. 357.—Lachnus strobi, and its two “honey” warts.—Gissler del.
Busgen, after careful research, denies that this is a sugar, but claims as the result of chemical analysis, that it is more like wax. He observed that on reaching the air the drops issuing from the “nectary” or “honey” tube stiffened almost instantly into a wax-like mass, which was easily crushed between the teeth, and had no taste at all. No sugar-like substance or urea could be detected. He therefore concludes that the secretion in question should be regarded as a wax-like mass, which agrees well with Witlaczil’s anatomical observations, and confirms the statements of previous observers. Thus, as early as 1815, Kyber stated that the Aphides expelled an excrementitious substance through the “sap tubes.” Burmeister states that the tubes give out a fluid which “dries gumlike, but, so far as I have observed, has no peculiar taste.” Réaumur, and also Kaltenbach, state that the “honey” does not issue from the tubes, but from the anus. Lastly, Forel emphatically states that “the two dorsal tubes of Aphides do not secrete a sweet fluid, but a gluey wax, which is not sought by the ants. Moreover the shield-lice and many leaf-lice have no such tubes, but yet are often sought by ants. The drops of sugar which the ants lick up are rather the excrement of the insects in question.” Hence the opinion first stated by Linné, that a sweet fluid is secreted by Aphides, must be abandoned.
On the other hand, Busgen, after careful observations, finds that the use of the sticky, waxen secretion is in reality a protective one, as he observed that when a larval Chrysopa rudely attacks the Aphides, they smear its face with the sticky wax, causing at least a momentary interruption in its attacks. He also observed that Aphides when invaded by coccinellid larvæ set their tubes in motion and besmear their heads and front part of the body. He thus seems to establish the fact that these tubes secrete a protective, sticky fluid.
i. Dermal glands in general
We have seen that certain of the hypodermal cells may be modified or specialized to form secretory unicellular glands. Such are those (trichogens) which secrete chitinous setæ, hairs, and spines, certain setæ in some insects being hollow and containing a poison (p. 187); others secrete wax, certain ones in Aphids “honey-dew”; in some cases dermal glands may excrete protective, sticky, or otherwise offensive matters, or may be depuratory, or facilitate the process of moulting.
There are other minute, unicellular, or compound dermal glands whose function is unknown.
Dermal glands may be segmentally or serially arranged. Thus Verson has detected a series of one or two pairs of unicellular glands near the stigmata in each thoracic, and the first eight abdominal segments of the silkworm (B. mori). In the earliest stages of growth of the caterpillar they give out oxalate of lime, and in later stages uric acid. They thus appear to act interchangeably with the urinary tubes, as excretory organs. They do not, however, carry their products directly outwards, but leave them between the hypodermis and cuticula, in order to facilitate the sloughing off of the latter in the process of moulting.