Behavioural interactions between co-habiting females and their impact on productivity and offspring sex ratios in the coffee berry borer, Hypothenemus hampei

1. The coffee berry borer (CBB) Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae) has invaded all coffee-producing regions of the world and causes substantial economic losses every year. A single female beetle typically infests one coffee berry, which her offspring consume over the course of development. Offspring then engage in sib-mating before daughters fly off to infest new berries.2. We assessed infestation rates across different locations in Jamaica and found a strong positive correlation between double infestation and overall infestation rate, suggesting that females prefer to breed alone but will tolerate sharing a berry under resource constraints.3. Using an artificial habitat to study productivity and behaviour in the laboratory, we found that single females produced significantly more offspring per capita than two females, suggesting that co-habitation is costly. Accordingly, co-habiting females spent a significant proportion of their time engaged in antagonistic interactive behaviours such as pushing. When daughter beetles were given the opportunity to stay with their mothers or to infest a new berry, they tended to leave.4. In contrast to some related beetle species, which exhibit gregariousness and even cooperative behaviour, beneficial social interactions in the CBB appear to be limited to parental care.