Effects of maternal age and adult diet on egg weight in the butterfly Euphydryas editha

ABSTRACT. 1. Euphydryas editha (Boisduval) (Nymphalidae) butterflies exhibited no consistent pattern of change in egg weight over their lifetimes. This was the case for captive butterflies fed diets containing sugars and amino acids, for butterflies fed diets containing only sugar, and for those left completely at liberty in their natural habitats between ovipositions. 2. Two aspects of these results conflict with the findings of a previous study on the same subspecies. First, the previous study found that egg weight decreased with increasing maternal age. Second, this decrease was mitigated by addition of amino acids to the adult diet. 3. We accept the findings of these previous workers that egg weight decreased with maternal age under their laboratory conditions. The discrepancy between their data and ours is likely to stem from the more natural conditions under which our insects were kept. Our own data from captive insects are not distinguishable from our field data. 4. These results suggest that declines of egg weight with maternal age found in studies of other insects may also result from the artificial nature of laboratory conditions. We question whether such declines are general. 5. We suggest that the second discrepancy between the two sets of work (effects of amino acids) stems from a design problem in the previous study.