Comparative studies with Tribolium (Coleoptera, Tenebrionidae)—I: Productivity of T. castaneum (Herbst) and T. confusum Duv. on several commercially-available diets

Abstract

Productivity (measured as the number of adult progeny produced in a given interval by a number of females) and relative developmental rates (the number of adult progeny found at specific intervals) have been determined for T. castaneum and T. confusum on a variety of different media. The media tested were flours of corn (C), rice (R), soy (S), whole wheat (W), a mixture of corn, rice, soy and whole wheat flour (M), white wheat (WW) and brown rice (BR) with and without a supplement of brewer's yeast. In T. confusum the ranking of productivity on these seven media was found to be M>W>C>BR>R>WW>S in both unsupplemented and yeast-supplemented media, but the performance on all media was somewhat increased by the addition of yeast. The order of productivity on these media with T. castaneum was similar to that obtained for T. confusum, except that the response to yeast supplements was much more pronounced for all media except soy. In particular, white wheat, brown rice and rice, which must be considered “poor” media for T. castaneum in the absence of yeast, compared very favorably, in terms of productivity, with whole wheat and corn when these media were supplemented with yeast. These data are summarized in Table 6 and Fig. 1. These productivity results are supported by information obtained about the developmental rates of the two species on these media-in general, developmental rate was much slower on those media showing the lowest productivity. From considerations of the content of the flours used, the data suggest that soy is more toxic to T. castaneum than to T. confusum, and that T. castaneum requires more vitamins and/or minerals than does T. confusum. This conclusion is largely judged by the performance of the two species on white and brown rice, and their performance on yeastless and yeast-supplemented media. The data are given in Table 5 and shown in graph form in Fig. 2. It is suggested that T. castaneum may require greater amounts of leucine, alanine, and aspartic acid than T. confusum, and that T. confusum requires larger amounts of threonine, tyrosine and possibly methionine than T. castaneum.