In cockroach, larval and nymphal characters are maintained by

Juvenile hormone is produced by corpora allata in insects, it favours the development of juvenile characteristics. During larval life, this hormone predominates and each moult yields another larger juvenile and keeps the larva in immature condition or maintains juvenility.Ecdysone is a steroidal, moulting hormone of the prothoracic glands, named "ecdysone" in insects that triggers metamorphosis.Salivary glands are the merocrine or epicrine type of gland. Their secretion diffuses out through the cell surface, causing no damage to the cell. In man, 3 pairs of salivary glands are present and in rabbit, they are 4 pairs. Salivary glands are absent in frog.Parotid glands are compound tubulo-acinar glands and are the type of salivary glands with a flask-like secretory portion. Poison gland of a toad is modified parotid gland. In rabbit, parotid glands are the largest salivary gland, present beneath the ears. Duct of parotid gland is known as Stenson's duct in man.