Garman, H. On a singular gland possessed by the male Hadenœcus subterraneus. (Psyche, 1891, p. 105, 1 Fig.)
Barrett, C. G. Scent of the male Hepialus humuli. (Ent. Month. Mag., Ser. 2, iii, 1892, p. 217. Arises from the curiously aborted and altered hind tibiæ.)
Also the writings of Baillif, Duponchel, F. Müller, Scudder (Psyche, iii, p. 278, 1881), Burgess, Keferstein, Alpheraky, Plateau, Marshall and Nicéville, Wood-Mason, White, Hampson.
THE ORGANS OF CIRCULATION
Although Malpighi was the first to discover the heart in the young silkworm, it was not until 1826 that Carus proved that there was a circulation of blood in insects, which he saw flowing along each side of the body, and coursing through the wings, antennæ, and legs of the transparent larva of Ephemera, though three years earlier Herold demonstrated that the dorsal vessel of an insect is a true heart, pulsating and impelling a current of blood towards the head. This discovery was extended by Straus-Dürckheim, who discovered the contractile and valvular structures of the heart. It is noteworthy that both Cuvier and Dufour denied that any circulation, except of air, existed in insects; and so great an anatomist as Lyonet doubted whether the dorsal vessel was a genuine heart, though he pointed out the fact that there are no arteries and veins connected with this vessel. Another French anatomist, Marcel de Serres, thought that the dorsal vessel was merely the secreting organ of the fat-body.
The so-called peritracheal circulation claimed by Blanchard and by Agassiz has been shown by McLeod to be an anatomical impossibility, the view having first been refuted by Joly in 1849.
Except the aorta-like continuation in the thorax and head which divides into two short branches, there are, with slight exceptions (p. 405), no distinct arteries, such as are to be found in the lobster and other Crustacea, and no great collective veins, such as exist in Crustacea and in Limulus. This is probably the result of a reduction by disuse in the circulatory system, since in myriopods (Julidæ and Scolopendridæ) lateral arteries are said to diverge near the ostia.
a. The heart
The heart or “dorsal vessel” is a delicate, pulsating tube, situated just under the integument of the back, in the median line of the body, and above the digestive canal. It can be partially seen without dissection in caterpillars. It is covered externally and lined within by membranes which are probably elastic; and between these two membranes extends a system of delicate muscular fibres, which generally have a circular course, but sometimes cross each other. The heart is divided by constrictions into chambers, separated by valvular folds. The internal lining membrane referred to forms the valvular folds separating the chambers. Each of these chambers has, at the anterior end, on each side, a valvular orifice (Fig. 370, ostium, i) which can be inwardly closed.
Miall and Denny thus describe the different layers of the wall of the heart of the cockroach: