Adaptive Value of Aggregation Behavior in the Fire Bug Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)
The adaptative value of aggregation behavior was examined in the gregarious fire bug, Pyrrhocoris apterus Linnaeus 1758. Up to 8 larvae per 132 cm2 test box, the rate of larval growth and development and the fecundity of the descendants were not affected compared with solitarily reared conspecifics. At 16 individuals per test box, however, larvae entered significantly faster the adulthood than solitarily reared larvae. The faster development was not derived at the cost of a smaller adult body size. Compared with solitarily reared larvae, the number of eggs per F per day was adversely affected in groups of 16 individuals per test box. The concurrent increase in egg volume indicates a shift of the reproductive investment towards offspring with a higher competitive quality rather than a simple decrease in the reproductive capacity. A further increase of the group size (32 L5 per test box) resulted in significantly smaller descendants with a reduced fecundity of the FF.