Embryology of insects and myriapods; Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching embryologyofinse00joha Year: 1941 256 EMBRYOLOGY OF INSECTS AND MYRIAPODS ment proceeds, attaining the region of the metathorax. On the bhnd end of the proctodaeum the buds of four Malpighian tubules appear which reach a considerable length before the hatching of the insect. They form as solid strands which later acquire a lumen. The reproduc- tive organs are not recognizable as such until the revolution of the embryo.
Embryology of insects and myriapods; Embryology of insects and myriapods; the developmental history of insects, centipedes, and millepedes from egg desposition [!] to hatching embryologyofinse00joha Year: 1941 256 EMBRYOLOGY OF INSECTS AND MYRIAPODS ment proceeds, attaining the region of the metathorax. On the bhnd end of the proctodaeum the buds of four Malpighian tubules appear which reach a considerable length before the hatching of the insect. They form as solid strands which later acquire a lumen. The reproduc- tive organs are not recognizable as such until the revolution of the embryo. What Melnikow (1869) considered to be the germ cells at the posterior end of the egg was probably the mass of symbionts. After revolution a small ventrally located anlage of the genital ducts is formed which remains at this stage of development until the first larval instar. The visible differentiation of the germ cells apparently occurs in larval life. Fig. —Pediculus. Sagittal section of caudal end. {am) Amnion, {mge) Mid-gut epithelial rudiment, {prod) Proctodaeum. {ser) Serosa. The mouth parts in the fully developed embryo, according to Scholzel (1937), are readily homologized with those of the adult. The ventral 'bristle,' provided with a lumen, is developed from the second maxillae. From the hypopharynx there is developed the 'dorsal bristle' of Vogel or sucking tube of Sikora and a ventrally located thin sclerotized tube, designed as the 'middle bristle' by Vogel or the 'salivary duct' by Sikora. Dorsad of the bristles is the anterior part of the pharynx with its dilator muscle. The first maxillae are, according to Scholzel, greatly reduced. Fernando (1933), however, considers the dorsal stylet as developing from the first maxillae, whereas the salivary duct alone is derived from the hypopharynx. MALLOPHAGA, THE BITING LICE The eggs of the Mallophaga are uniformly smaller than those of the Siphunculata and are rather variable in form. The species parasitic on m
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