Fig. 557.—Head of freshly hatched larva of Pulex canis: eb, hatching spine; ant, antennæ; md, mandible; mx, maxilla; mx′, 2d maxilla; lbr, labrum.
The hatching spine of Pulex canis (Fig. 557) is a thin vertical plate, like the edge of a knife, situated in the median line of the head very near the posterior end, and is somewhat cultriform, the upper edge slightly hollow, and turned up a little at the anterior end. Though we did not see it working, it is situated at just the point on the head where it would come in contact with the egg-shell, and it was evident that the larva, by moving its head back and forth, would produce a slight split in the chorion and cause it to burst asunder. Later on in larval life it disappears, probably at the first moult.
LITERATURE ON EMBRYOLOGY
Koelliker, Albert. Observationes de prima insectorum genesi, etc. Turici, 1842, pp. 29, 3 Pls.
Rathke, H. Zur Entwickelungsgeschichte der Maulwurfsgrille (Gryllotalpa vulgaris). (Müller’s Archiv, 1844, ii, p. 27, Figs. 1–5.)
Zaddach, G. Untersuchungen über die Entwicklung und den Bau der Gliederthiere. I. Die Entwicklung des Phryganideneies. Berlin, 1854, pp. 138, 5 Taf.
—— Ueber die Entwicklung der Insekten. (Schrift, d. k. phys.-oekon. Gesell. Königsberg, viii Jahrg., 1867, Sitzb., p. 16.)
Leuckart, Rudolph. Die Fortpflanzung und Entwicklung der Pupiparen. Nach Beobachtungen an Melophagus ovinus. (Abhandl. Naturf. Gesell. Halle, iv, pp. 1–82, 3 Taf.) Halle, 1858.
Huxley, T. H. On the organic reproduction and morphology of Aphis. Pt. I, 1858; Pt. II, 1858. (Trans. Linn. Soc., xxii, pp. 193–219, 221–236, 5 Pls.)