Material Benefits from Multiple Mating in Female Mealworm Beetles (Tenebrio molitor L.)

In yellow mealworm beetles (Tenebrio molitor), females are sexually receptive throughout their adult lives. We examined how access to mates affected female fecundity by varying the number of matings per female and quantifying cumulative egg production. Also, we dissected females at successive intervals after a single mating to assess the relationship among time since mating, sperm supplies, egg load, and oviposition rate. Females that mated at intervals greater than 2 days did not produce as many eggs as females that mated every 2 days or were allowed to mate ad libitum. Dissections showed that the amount of sperm remaining in a female spermatheca was correlated with the number of eggs she had laid recently, which suggests sperm replenishment as the material benefit gained through multiple mating. However, females mate more frequently than necessary for sperm replenishment, and therefore material benefits alone may not fully explain the continuous receptivity of T. molitor females.