Carlet, G. Sur les organes sécréteurs et la sécrétion de la cire chez l’Abeille. (Comptes rendus, cx, pp. 361–363, 1890.)
—— La cire et ses organes sécréteurs. (Le Naturaliste, 1890, pp. 149–151, 2 Figs.)
Also the works of Siebold, Cheshire, Kolbe, Howard and Marlatt (Bull., 3, N. S., Div. Ent. U. S. Dept. Agr., 1896, p. 40), Knaggs, Berlese.
d. Wax-like glands of Aphides
Huber et Forel, A. Études myrmécologiques, 1875.
Witlaczil, E. Zur Anatomie der Aphiden. (Zool. Anzeiger, v Jahrg., 1882, pp. 239–241; Arbeiten a. d. Zool. Institut der Univ. Wien., iv, 1882, pp. 397–441, 3 Taf.)
Busgen, M. J. Der Honigtau. Biol. Studien an Pflanzen u. Pflanzenlause. (Jena. Zeitschrift, xxv, 1891, pp. 339–428.)
DEFENSIVE OR REPUGNATORIAL SCENT-GLANDS
While these eversible glands are not found in marine or aquatic arthropods such as Crustacea or Merostomata (Limulus), they are often present in the air-breathing forms, especially insects. In the winged insects they are of frequent occurrence, existing under great variety of form, varying greatly in position, and appearing usually to be in immediate relation with their active volant habits. Their presence is in direct adaptation to the needs and habits of their possessors, and being repellent, warning, or defensive structures, the odors they secrete being often exceedingly nauseous, they appear to have been called into existence in direct response to their biological environment. The fact that these singular organs do not exist in marine or aquatic Crustacea suggests that the air-breathing, aërial, or volant insects by these eversible glands, usually in the form of simple evaginable hypodermic pouches, are enabled to protect themselves by emitting an infinitesimal amount of an offensively odorous fluid or ether-like spray which charges the air throughout an extent of territory which may be practically illimitable to the senses of their enemies. The principle is the same as in the mephitic sulphuretted oil ejected by the skunks, the slight quantity these creatures give out readily mixing with and charging the atmosphere within a radius of many miles of what we may call the centre of distribution.
As is now well known, the very delicate, attenuated highly volatile odors exhaled are perceived by insects with extreme ease and rapidity, the degree of sensitiveness to such scents being enormously greater than in vertebrates, their organs of sense being developed in a corresponding degree. Professors Fischer and Penzoldt, of Erlangen, have recently established the fact that the sense of smell is by far the most delicate of the senses. They find that the olfactory nerve is able to detect the presence of 1
2,760,000,000 of a grain of mercaptan.[[58]] The smallest particle of matter that can be detected by the eye is sodium, when observed by the spectroscope, and this particle is 250 times coarser than the particle of mercaptan which can be detected by the human nose.