Requirement of the Flour Beetle (Tribolium confusum Duval) for Vitamins in the B Group

Abstract

Insects offer certain possibilities for vitamin assay. If the vitamin requirements of certain insects were known it should be possible to assay vitamins with much less time and labor than with rats or similar animals. A suitable insect for nutritional research is the flour beetle, Tribolium confusum Duval.

When raised on whole wheat flour at 32° and 70% humidity, the larvae transform to the pupal stage in an average time of 16 days. Sweetman and Palmer 1 found that on a diet of purified food materials devoid of all vitamins the insects did not pupate. The addition of a small amount of material containing the vitamin B complex enabled the larvae to pupate in a normal time.

The renewed interest in methods for assay of the vitamins in B group brought about by the recent advances in the chemistry of these substances prompts us to report briefly experiments conducted by us in 1931-32. In this study an attempt was made to determine which members of the vitamin B complex are necessary for Tribolium. A basal diet of casein 15, crisco 3, Osborne-Mendel salt mixture 4, dextrin to 100 was used. Various vitamin supplements were added to 5 gm. quantities of the basal diet, and the food was placed in a vial with 20 two-hour-old larvae. The vials were kept in a temperature cabinet at 32°C. and 70% humidity and the average time of pupation recorded. A vitamin B₁ concentrate prepared from rice polishings was used. The average time required for pupation with the various supplements to the basal diet were: vitamin B₁ concentrate equivalent to 50% rice polish no pupation, 5% autoclaved yeast no pupation, 1% autoclaved yeast plus vitamin B₁ concentrate equivalent to 2% rice polish 19.2 days. This indicates that Tribolium requires a heat stable factor in addition to vitamin B₁. It was found that this heat stable factor was destroyed by autoclaving at pH 13 for 4 hours.