Effect of starvation and feeding of larvae during 4th stadia on pupation and adult size in Dacne picta (Coleoptera: Erotylidae).

Abstract

The effects of feeding and starvation during the 4th larval stadium on the later development of Dacne picta (Coleoptera: Erotylidae) were observed by rearing under various diet regimens on dried fruiting bodies of shiitake mushroom, Lentinula edodes. When the food was removed after different durations of feeding, pupation occurred at ca. 7 d after removal of the food resource irrespective of the duration of the feeding period. The body size of eclosed adults increased with longer feeding periods. We investigated the feeding response of larvae provided mushrooms as food after different durations of initial feeding and starvation periods. Two responses were observed. Larvae either resumed feeding on the mushrooms (re-feeding individuals) or did not resume feeding (non re-feeding individuals), and these patterns resulted in large and small adult size, respectively. Re-feeding during the larval stage only influenced the body size of individuals which had had short initial feeding and starvation periods, and the percentage of re-feeding individuals also decreased with the protraction of the initial feeding and starvation periods. Adult body size of non re-feeding individuals decreased with protraction of the starvation period between feedings. This indicates that the pupation of larvae depends on larval mass and duration of the starvation period. The threshold larval size of males at metamorphosis was significantly smaller than that of females. This pattern of larval growth and pupation of the beetles would be advantageous when completing immature development on a short-lasting food resource. Further, such size dependent pupation of larvae would result in larger size of females than males, and synchronization of pupation and eclosion.