Certain growth characters of Tribolium castaneum as modified by long term selection for 21-day pupa weight.

Seven related populations of Tribolium castaneum were compared to determine the effect that selection for increased 21-day pupa weight had on certain other aspects of growth.It was found that the response to selection for increased 21-day pupa weight had been accompanied by an increase in weight at all ages from day 6 to day 30, an increase in the growth rate during the larval period, and an increase in weight loss during the pupal stage. As a consequence, the shape of the growth curve was altered. The removal of selection pressure for six generations resulted in a decline in all of these parameters. The decline in weight was most pronounced at 21 days. Overall, it appeared that the shape of the growth curve was reverting to the shape found in the unselected populations.Comparisons between the select line and a reconstructed base population indicated no significant difference in egg weights or weight on day of hatch. The select line had significantly fewer larval molts and less variability in time of molting.