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5. External Genitalia
Female. These consist of the vulva, or genital aperture, the subgenital plate, and three pairs of processes, the gonopophyses or valvulae, which together form the ovipositor. The genital aperture is situated on the seventh abdominal sternum (Fig. 24, S. VII) and is covered by the subgenital plate (Sgp) which is a backward prolongation of the sternum. The dorsal valvulae (Figs. 25, 26, Dv) are the longest and overlap the ventral ones (Figs. 24, 26, VV), the tips of which curve up to meet them. The inner valvulae (Fig. 27, IV) he alongside the inner faces of the ventral ones, but are much shorter than either of the other two pairs. There is very little difference in the length of the dorsal and ventral valvulae and they are approximately the same length as the body from vertex to anus. The dorsal and ventral valvulae completely enclose the inner valvulae.
The Rhaphidophoridae are regarded as possessing some of the most primitive types of ovipositors. In Macropathus filifer the ovipositor is approximately ovoidal at the base and the blades become increasingly compressed distally. Each dorsal valvula possesses a hook. (Fig. 27, H) on the ventral surface for sliding over the serrated chitinized outer edge of the corresponding ventral valvula so that the valvulae do not part company, but are held together and their only movements are backwards and forwards. The dorsal valvulae meet along their mid-dorsal line, the ventral valvulae along their mid-ventral line. The ovipositor is roughly sabre-shaped with a marked dorsal curve. In the young animal the developing ovipositor is a creamy colour and very soft; but as it develops the colour intensifies to a deep red brown at the tip and round the edges of the valvulae. When the colour is fully developed the animal is sexually mature. With the deepening of colour, chitin is deposited most strongly round the edges of the dorsal and ventral valvulae. The inner valvulae are white with a thin band of chitin, the rami (Fig. 27, Riv), round their edges These are connected by a strengthening bar, the pons valvularum (Figs. 27, 28, 29, Pv), which extends across the intervalvular membrane (Figs. 27, 29, Im), a fold of integument connecting the inner valvulae for a short distance from the base. Between the bases of the dorsal valvulae and fused with them is a median sclerite, the superior intervalvula (Figs. 28, 29, Si), which bears a median vertical apodeme (Fig. 28, Ma) for attachment of the principal muscles concerned with the movements of the ovipositor. Another median sclerite, the inferior intervalvula (Figs. 27, 29, II), is situated on the ventral surface at the base of the intervalvula membrane. The rami of the inner valvulae are connected with the inferior intervalvular and also with the inferior apophysis (Figs. 27, 29, Iap), a ventral process arising from the base of each dorsal valvula. A similar larger process,
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Text-Fig. 5. External Genitalia. Female. Fig. 24—Ventral view terminal abdominal segments. Fig. 25—Dorsal view terminal abdominal segments Fig. 26—Lateral view terminal abdominal segments. Fig. 27—Ventral view, valves of ovipositor opened out showing supporting apodemes Fig. 28—Dorsal view, valves of ovipositor opened out showing supporting apodemes Fig. 29—Posterior interior view terminal abdominal segments, showing skeletal structure of genitalia
Ap VIII IX, X apodemes of pleinites VIII IX, X. AS VIII, IX, poorly chitinized apodemes of sternites VIII, IX; At VIII, IX, X, apodemes of tergites VIII, IX, X, Av, apodeme of ventral valve, B, basivalvula, Bc, basal segment of cercus, C, cercus. Dv, dorsal valve, Fo, fenětres ovales II, hook. for articulation with vential valve, Ia, intersegmental apodeme, Iap, inferior apophysis, II, intervalvula, Im, intervalvular membrane, IV, inner valve, Ma, median apodeme, Mt IX membrane tergite IX, P, VII, VIII, pleurite VII, VIII, Pm, perianal membrane, Pp, paraproct, Pv, pons valvularum, Riv, ramus of inner valve, S. VI, VII, sternite VI, VII, Sa, superior apophysis, Sap, supra-anal plate, Sgp, subgenital plate, Si, superior intervalvula, Sp, spiracle, T. VI, VII, VIII IX, X, tergite VI, VII, VIII, IX, X, 1Vf, first valvifer, 2Vf, second valvifer, VV, ventral valve
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the superior apophysis (Figs. 28, 29, Sa), projects forward into the haemocoele from the dorsal basal region of each valvula. Both these pairs of apophyses serve for muscle attachment.
The inner valvulae roof over the passage along which the eggs are passed.
The ventral valvulae arise from the posterior margin of the eighth sternum. Each consists of a short basal segment, the basivalvula (Figs. 24, 26, 27, B), and a longer shaft The basivalvulae are distinct, though not heavily chitinized, and are not wholly concealed by the rather small subgenital plate. Between the basivalvula, the ninth tergite (Fig. 24, T. IX) and the base of the dorsal valvula is the subtriangular first valvifer (Figs. 24, 26 1Vf). Dorsal to this is the second valvifer (Figs. 24, 26, 2Vf). These valvifers form the antero-lateral part of the ninth sternum.
The broad proximal portion of the dorsal valvulae passes imperceptibly into a longer, more slender, distal portion not separated by a suture so that no basivalvulae are recognisable.
The eighth sternum is prolonged caudad as the subgenital plate covering the vulva and bases of the ventral valvulae. On the ventral surface of the subgenital plate is a flap of tissue closing the aperture of the genital chamber. The sub-genital plate (Fig. 24 Sgp), which is obtuse-angled laterally, and deeply emarginate distally, appears constant in shape in all the animals I have examined. It is thickly clothed with setae.
The supra-anal plate (Fig. 25, Sap), though well developed, is not divided transversely into two sclerites—i.e., there is no separate eleventh tergite and the plate is not sharply marked off from the tenth tergite (Fig. 25, Tx). The shape of the supra-anal plate is not constant but varies between two extremes, one of which is rounded and notched in the centre (Fig. 28, Sap), while the other is obtuse-angled laterally and truncated terminally (Fig. 25, Sap). Many intermediate stages occur, some straight, some slightly concave, and others slightly convex.
The paraprocts (Fig. 25, Pp) are well developed, but little chitmized, and are clothed with brown setae.
The long, flexible cerci (Figs. 24, 25, C) taper from a stout base to a slender apex. There is a basal segment (Fig. 25, Bc) at the base of each cercus. The cerci are clothed with long and short setae and are similar in both sexes.
Male. The supra-anal plate (Fig. 31, Sp) is well developed and fused with the tenth abdominal tergite (Tx). As in the female its shape is not constant. It may be either concave or convex terminally or of an intermediate stage between these two extremes. The ninth sternum (Fig. 30, S Ix) is undivided, and on each side disto-laterally bears a terminal stylus (Figs. 30, 31, S). The cerci (Figs. 30, 31, C), which are as already described for the female, are not modified to function as claspers.
Situated in the large membranous area between the paraprocts (Figs. 31, 32, Pp) and the ninth sternum is the penis (Fig. 32, Pn). This organ itself is almost entirely membranous and is divided into four lobes, two dorsal and two ventral. On the tips of the two upper ones are the openings of the male genital ducts (Fig. 32, Op), clearly demarcated by their chitinized margins. Arched over the base of the penis is the hood-like pseudosternite (Fig. 32, Pd) the cavity of which forms a sheath into which the penis may be retracted. It serves for the insertion of muscles concerned with the movements of the penis
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Text-Fig. 6 External Genitalia, Male Fig. 30—Ventral view gemtalia Fig. 31—Dorsal view gemtalia. Fig. 32—Ventral view gemtalia—hypandrium removed to expose structure beneath Fig. 33—Posterior interior view of terminal abdominal segments showing skeletal structure of gemtalia
Abc, apodeme of basal segment of cercus; Abs, apodeme of basal segment of stylus, Aep apophysis of endoparamere, Ap, apodeme of paramere, App, apodeme of paraproct, Bc, basal segment of cercus, C, cercus, Cpd, chitmous structure of pseudo-sternite, Ctp chitinized tubes of penis; De, ductus
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. E, endopophysis, Ep, endoparamere. Fca, feebly chitmized arch connecting rami; H, hypandrium (subgemtal plate); Mr, muscle attached to ramus, Ms VIII, IX, membrane sternite VIII, IX; Mt VIII, IX, membrane tergite VIII, IX, Op, opening of penis, P, paramere (ectoparamere), P. VIII, IX,
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unclear:
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VIII, IX, Pd, pseudosternite, Pn, penis, Pp. paranal plate (paraproct); Rp, rami of pseudosternite, S, stylus, S. VIII, IX sternite VIII. IX, Sp, supra-anal plate; Spi, spiracle, T. IX, X, tergite IX, X, Tv, tube of vesiculae seminales
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This arch is prolonged on each side into a pair of arms, the rami (Fig. 32, Rp), which are connected with one another ventrally by a feebly chitinized arch (Fig. 32. Fca). The rami are produced inwardly into two processes, the endapophyses (Fig. 32, E), which are large and well developed and serve for the attachment of further muscles controlling the movements of the penis.
The parameres (Figs. 31, 32 P), which are dorso-terminal in position, are chitinized more heavily on their outer sides and their inner surfaces are thickly clothed with long brown setae. At the tip of each paramere is a dark brown spot of chitin. The upper external portion of the paramere is the ectoparamere. The bases of the parameres unite to form a plate, the endoparemere (Fig. 32, Ep), attached to which, on either side of the pseudosternite, is an apophysis (Fig. 32. Ap).
On either side of the parameres and beneath the supra-anal plate lie the paraproets, which are lobe-like structures, but little chitinized and clothed with brown setae.
The hypandrium (Fig. 30, H) (subgenital plate) is part of sternite nine and bears two short, stout styli clothed with short brown setae. The hypandrium covers over all the gemtalia except the parameres. The tip of the ventral surface of the hypandrium is brush-like, thickly clothed with brown setae, and projects beyond the dorsal surface of the plate.