Egg weight variation in relation to egg mortality and starvation endurance of newly hatched larvae in some satyrid butterflies

Abstract. 1. Egg weights decrease over the oviposition period in all of the five satyrid butterflies that have been studied, viz Parage aegeria L., Lasiommata petropolitana F., L.maera L., L.megera L. and Lopingaachine Scop. However, within each species, no correlation was found between variation in egg weight and egg mortality in 30% relative humidity or the ability of newly hatched larvae to survive without food for 1–4 days. 2. Although egg weights of Papilio machaon L. were similar to the highest satyrid egg weights, newly hatched larvae of P.machaon showed significantly higher mortality after 1 day of starvation when compared to all of the satyrid larvae. This indicates that the capability of newly hatched larvae to endure starvation is not necessarily correlated with egg weight, and consequently that this character trait of satyrid larvae has been selected for (i.e. should be regarded as an adaptation). It is noteworthy that this ability of satyrid larvae to endure starvation is coupled with the habit of many satyrid butterflies not to deposit their eggs directly on the larval host plants. 3. In 30% relative humidity, egg mortality of L.achine was 100% and that of P.aegeria 29.2%, whereas that of the three Lasiommata spp. was significantly lower. At 100% relative humidity egg mortality in L.achine dropped to 8%. Since egg weights are higher in L.achine than in the other four satyrids this indicates that egg resistance to desiccation is not necessarily correlated with egg size (as might be expected due to the area to volume ratio which is negatively correlated with egg size). Thus the resistance to desiccation which is found in the three Lasiommata spp. should be regarded as an adaptation to the habit of these three butterflies to deposit their eggs in relatively dry microhabitats. This resistance to desiccation is not found in eggs of the two forest-dwelling satyrids P.aegeria and L.achine which lay their eggs in microhabitats where the relative humidity is high.