The Development of the Midgut in the Larva of Aedes Dorsalis Meigen

Abstract

It is common knowledge that insect larvae are usually adapted for efficient food acquisition. Adults are specialized for reproduction. Nutritive materials accumulated by the larvae are utilized during metamorphosis for energy of transformation from larva to imago. Attempts to explain the manner in which the larval stored foods are utilized have not always been strictly accurate. One of the best explanations stresses the importance of digestion of larval tissues and subsequent replacement by imaginal tissue developed from regenerative buds or nuclei. Trager (1937), working with Aedes aegypti , says that trichogenous cells, anal gills, foregut, midgut, colon, salivary glands, large oenocytes, main tracheal trunks and longitudinal abdominal muscles of the larva are destroyed during the pupal stage or shortly after. Larval hypodermis, fat body, thoracic ganglia, Malpighian tubules, heart and pericardial cells persist essentially unchanged into the adult. Woolley (1943) and Christensen (1941) find no evidence of histolysis in the nervous system and the internal reproductive system respectively of Aedes dorsalis . Richins (1938) finds in the midgut of this same species, however, a striking example of larval tissue degeneration with replacement by imaginal buds.