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The majority of adults from 12 laboratory strains of flour beetles (Tribolium castaneum), and a synthetic strain produced by crossing them together, preferred wheat flour when given a choice of 2, 4, or 6 diets (all of which supported survival and reproduction). Sixteen generations of selection on 5 different diets did not alter this behavioral response, which seems to be fixed in Tribolium. Zusammenfassung Über die Anlockung von Mehlkäfern, Tribolium castaneum (Herbst) (Col., Tenebrionidae): Erbliches Verhalten oder „Konditionierung”? Die Mehrzahl der Adulten von 12 Laborstämmen von T. castaneum sowie von einem synthetischen Stamm aus der Kreuzung zwischen den anderen Stämmen, zogen Weizenmehl vor, wenn sie die Wahl zwischen 2, 4 oder 6 verschiedenen Diäten hatten, welche alle das Überleben und die Reproduktion gewährleisteten. Sechzehn Generationen aus Zuchten an 5 verschiedenen Diäten änderten diese Verhaltensweise nicht, die somit bei Tribolium erblich fixiert scheint.

Five populations derived from a composite, genetically heterogeneous strain of the flour beetle, Tribolium castaneum, were selected on new diets (dog food, powdered rice, brewers' yeast, wheat flour and oats) for 13 -16 generations. A control population was reared on the standard medium (flour + 5°7o brewers' yeast). Adaptedness was measured in terms of (1) fitness parameters (survival and developmental time), (2) amylase activity levels (amylase is an essential digestive enzyme in flour beetles) and (3) food preference behavior.There were significant temporal trends in fitness components in the selected populations. Survival was initially low but increased with time. Developmental time decreased in later generations of selection. The control population showed the smallest increase in survival and no decrease in developmental time. When tested at the end of the experiment, survival to adulthood of eggs from each selected population on its selective diet was higher than that of control eggs. On the standard medium, no differences in survival among populations were detected. These results suggest that the improvement in fitness may indicate adaptation to the new environments created by the different food media.Amylase activity also increased temporally in 4 selected populations but not in the control (nor on unenriched wheat flour). Tests at the end of the experiment, however, suggest that this increase was, in large part, environmentally induced. We found no evidence that an adaptive genetic change in amylase regulation took place.There were no temporal trends in food-preference behavior during the selection process.

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Females of three mutant strains of Tribolium castaneum were mated in sequence to two different male genotypes. The second male sired most of the offspring in each sample, but some of the first male's progeny were often present, particularly in the first 3 days of exposure to the second male. We believe that this is the result of oviposition of fertilized eggs before copulation with the second male. This explanation is supported by the fact that quantitative differences in the proportion of “old” sperm in the different strains correspond to their relative mating speed. ZUSAMMENFASSUNG NEUE INFORMATIONEN ÜBER DIE SPERMIENFOLGE BEI WIEDERHOLTER PAARUNG VON TRIBOLIUM‐KÄFERN Weibchen von drei mutierten Stämmen von Tribolium castaneum wurden nacheinander mit zwei verschiedenen männlichen Genotypen gepaart. Bei jedem Versuch stammten die meisten Nachkommen vom zweiten Männchen. Oft waren aber einige Nachkommen des ersten Männchens vorhanden, besonders in den 3 ersten Tagen der Exposition zum zweiten Männchen. Wir nehmen an, dass dies das Resultat der Eiablage von befruchteten Eiern vor der Kopulation mit dem zweiten Männchen ist. Diese Erklärung wird dadurch gestützt, dass der Anteil an “alten” Spermien bei den verschiedenen Stämmen ihrer relativen Kopulationsgeschwindigkeit entspricht.