The vitamin B-complex requirements of several insects

It has been shown by us [Fraenkel & Blewett, 1943b] that six insects, which normally feed on flour and other dried food, grow satisfactorily on a diet of casein 50, glucose 50, yeast 5, cholesterol 1, McCollum's salt mixture 1, and water 15 parts, but entirely fail to grow when yeast is omitted. With the yeast replaced by yeast extract, the growth rate is considerably slower. No growth takes place if the diet contains a water-insoluble fraction alone in place of whole yeast. Previous work has indi- cated that insects require several vitamins of the B-group; the position up to 1940 has been reviewed by Craig & Hoskins [1940] and Trager [1941]. The present paper deals with the growth factors required by insects which are contained in the water-soluble and in the water-insoluble fractions of yeast. Short accounts of some of the results have already ap-