THE CHEMICAL NATURE OF GROWTH FACTORS REQUIRED BY MOSQUITO LARVÆ

I. RIBOFLAVIN AND THIAMIN

¹ From the Department of Animal and Plant Pathology, the Rockefeller Institute for Medical Research, Princeton, N. J., and the Department of Biological Chemistry, Harvard Medical School, Boston, Mass.

Riboflavin, and thiamin or certain of its degradation products, are necessary for the normal development of larvæ of the yellow fever mosquito Ædes ægypti. In the presence of all the other necessary growth factors, riboflavin permits normal larval growth at concentrations as low as 0.0004 mg. per ml. and has a definite effect at a concentration of 0.00008 mg. per ml., while thiamin permits normal growth at concentrations at least as low as 0.0008 mg. per ml. Although larval growth is normal in the presence of suitable amounts of heat-killed yeast, riboflavin, and the other liver extract factors supplied in partially purified form, metamorphosis to the adult stage is successfully accomplished by a relatively small percentage of the insects. If, however, the flavin is supplied as a flavin-purine complex containing 1.2 per cent flavin-phosphate, almost all the larvæ transform into vigorous adults. The nature of the additional factor responsible for this difference is not known.