Observations on the General Biology of the Flour Beetle, Tribolium Confusum

T KIBOLIUM CONFUSUM, the flour beetle, possesses characteristics which commend it to the attention of experimentalists. It is cosmopolitan and easily obtainable; it has a moderately short life-cycle; it is hardy and requires no elaborate equipment for its maintenance; both adults and immature forms are readily recoverable from the medium for study by a simple technique, and it spends its entire life-history in various pulverized grains such as flour. As has been pointed out before, this latter feature is particularly advantageous in many kinds of experimentation since, with a total environment such as flour, considerable stability of both intraand extramedium relationships can be obtained. By using similar flour in all experiments and by expressing this flour quantitatively in terms of weight and surface exposure, as well as surrounding the flour by as constant external conditions as obtainable, a total environment can be established which is relatively quite constant and reproducible. Despite these attractive requisites it is only recently that Tribolium has come to the attention of biologists interested in theoretical problems. The economic zoblogists have been vigorously aware of the existence of this form for many years and have done much in providing data on the general ecology of the species. However, past this point, these workers, possibly unfortunately, have seemed more interested in devising methods of exterminating the form than recommending it to the attention of experimentalists. Babcock (i9i2z), an early worker with Tribolium, used this beetle in studying the problem of metabolic water, finding the insect maintained a tissue water level about 40 per cent greater than the moisture content of an environment containing io per cent water. Davey (I9I7, 'I9), another early investigator, reported results showing that the length of life of these beetles could be prolonged if mass cultures received a small daily dosage of X-rays. Probably the principal credit in introducing Tribolium as an experimental organism, however, belongs to R. N. Chapman who in I9I8 reported on its life-history, in I9Z-4 on its nutritional requirements, and in i9z-8 on its suitability for population study. These papers will be discussed at length later: it is only important at this point to remember that they emphasized the practicability of Tribolium for experimental purposes by presenting a technique of handling the beetles as well as actual data. Since Tribolium does seem destined to merit more experimental attention, and since experimentalists need a factual background about the animal of their endeavors, it seems permissible at this stage to review fairly completely certain details about the flour beetle in the hope that such a review will be helpful and possibly stimulating to future investigators in the field. With this in mind the following general topics