The use of animal models for initially screening antiaging drugs is a promising approach for drug discovery. However, there a number of potential artifacts, confounds and errors that can arise in such research programs. The following rules are intended to minimize such problems: (1) since aging occupies an increasing proportion of human adulthood, data that conflate aging and late life should not be extrapolated to human aging; (2) the response to candidate medications should show a normal dose-response pattern, although not necessarily a linear response; (3) medicated animal models should not be hypometabolic; (4) medicated animal models should not show pronounced reductions in fertility; (5) medicated animal models should not exhibit general nervous system depression; (6) the effect of the medication should not be highly sensitive to the culture environment; (7) the effect of the medication should not be highly dependent on the genetic ancestry of the stock employed, leaving aside inbreeding, which should be avoided because humans are not generally inbred. While these rules do not guarantee successful extrapolation of successful drug results from the animal model to humans in a clinical setting, the failure to adhere to these rules should raise doubts about such extrapolation.

The evolution of foraging in Drosophila melanogaster (Meigen) is studied using outbred populations that had been differentiated using laboratory selection. The foraging behaviour of Drosophila larvae is measured using the foraging path length of 72-h-old larvae. The foraging path length is the distance travelled by foraging larvae over 5 min. Populations of Drosophila selected for rapid development show significantly greater path lengths than their controls. Populations of Drosophila selected for resistance to ammonia and urea in their larval food have shorter path lengths than their controls. Individuals in the ammonia-resistant populations are smaller than those in the control populations, but the size-adjusted metabolic rates are not significantly different. A simple model is proposed suggesting that changes in larval foraging behaviour may be a means for Drosophila larvae to adapt to new environments that require additional maintenance energy. In the ammonia-selected populations, crucial tests of these ideas will have to be conducted in environments with ammonia.