Collection of pupae
Time of larviposition was recorded, including whether or not larvae produced were viable (Baldry et al. 1992). Production of non-viable offspring was considered a spontaneous abortion (‘abortion’ hereafter). It was not possible to record egg abortions as they were not visible on the pupal tray due to their small size. For pupae collected at the start of the week (Monday morning), we consulted the last 72 hours of video recordings to determine the exact day of larviposition (S1 File). For aborted larvae, however, because of the small size of early larval stages, we could not determine the abortion date for those aborted over the weekend. Hence, they could have occurred on either Friday post-feeding, Saturday, Sunday or Monday pre-feeding. They were recorded as occurring on the Friday.
We measured the wet weight of pupae, to 0.1 mg, as an indicator of pupal size and therefore a proxy for maternal investment. Wet weight was previously found to correlate with pupal volume in field flies and does not require destructive sampling (Hargrove 1999). Of the pupae produced, we selected 70% of samples to track emergence, assigned using a random number generator in the data recording spreadsheet (Fig 1). The remaining 30% we destructively sampled for fat analysis in order to quantify how wet weight correlates with fat reserves.