ECOLOGY AND BEHAVIOR Increasing Coffee Berry Borer (Coleoptera: Curculionidae: Scolytinae) Female Density in Artificial Diet Decreases Fecundity FERNANDO E. VEGA, 1 MATTHEW KRAMER, 2 AND JULIANA JARAMILLO 3,4 J. Econ. Entomol. 104(1): 87Ð93 (2011); DOI: 10.1603/EC10353 ABSTRACT Three experiments were conducted to determine the inßuence of number of coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), females (one, two, or Þve) reared in artiÞcial diet on fecundity and subsequent development of larvae, pupae, and adults. Our results demonstrated that increasing female density from one to two or Þve individuals did not result in the expected two- or Þve-fold increase in progeny, despite ample food resources available. Instead, decreased fecundity was observed with increasing density for all experiments. The mechanism reducing fecundity was not identiÞed, but possibly, volatiles are being produced (e.g., host-marking pheromones). The decrease in fecundity may explain why infestations of only one colonizing female per berry are the norm in the Þeld. KEY WORDS artiÞcial rearing, bark beetles, Hypothenemus hampei, host-marking pheromones The coffee berry borer, Hypothenemus hampei (Fer- rari) (Coleoptera: Curculionidae: Scolytinae), is the most devastating insect pest of coffee (Coffea arabica L. and Coffea canephora Pierre ex Froehner) world- wide and has now been reported in most coffee-pro- ducing countries (Vega 2008). Damage begins after a female bores a hole in the berry and builds a gallery in the endosperm (i.e., seed), where eggs are depos- ited. After hatching, the larvae start consuming the seed (each coffee berry has two seeds), thus reducing both the yield and the quality of the marketable prod- uct. The larvae pupate within the berry, followed by sibling mating inside the berry, where there is a 10:1 sex ratio favoring females. Males never leave the berry, whereas inseminated females emerge and search for another berry in which to oviposit (Vega 2008). Fe- males can oviposit throughout their entire life span (Corbett 1933) and can live for up to 282 d (Bergamin 1943). In nature, coffee berries are attacked by only a single female (Jaramillo et al. 2006), and Þnding a berry bored by more than one female is rare (F.E.V., personal observation). The only report we are aware of where more than one female per berry is reported was written by Tothill (1940) about Uganda. He stated, “During intense infestation more than one fe- male beetle (with corresponding number of entrance holes) will attack a single berry and the damage is much accelerated.” One might argue that the number of coffee berries in a coffee plantation is not a limiting resource, and that this abundance explains the lack of multiple infestations per berry; i.e., with many berries and few beetles, if the femalesÕ distribution is random (counts per berry follow a Poisson distribution), the probability that berries harbor more than one female is low. However, if the limiting resource for a female and its progeny is the seed inside the berry, it is advantageous for a female (to maximize the survival of her brood) to be the sole colonizing female for that berry. Reports on the maximum number of eggs laid per female within a berry vary. Corbett (1933) re- ported 60 eggs; Bergamin (1943) found 74 eggs; and more recently, Jaramillo et al. (2009) reported nearly 300 eggs in a single berry. Thus, there is ample demand by the progeny for a limited resource, i.e., the en- dosperm, to complete development from egg to adult. Baker (1984) reported that Þeld infestations of the coffee berry borer tend to occur in aggregations, whereas Ochoa Milian and Decazy (1987) found that when infestations exceed 10%, the infestation is no longer aggregated and beetles infest berries at ran- dom. However, neither of the preceding two reports indicated that berries were infested by more than one insect, even under aggregated infestations. Working in Mexico, de Kraker (1988) conducted experiments that showed that infested berries seemed to repel other coffee berry borers. Vega et al. (2009) hypothesized that one possible explanation for the lack of multiple colonizing females inside one berry could be the pro- duction of a host-marking pheromone produced by the initial colonizing female. Other possible explana- tions are that female coffee berry borers avoid berries with a physical hole (bored by another female), that 1 Corresponding author: Sustainable Perennial Crops Laboratory, USDA-ARS, Bldg. 001, BARC-W, Beltsville, MD 20705 (e-mail: fernando.vega@ars.usda.gov). 2 Biometrical Consulting Service, USDAÐARS, Bldg. 007, BARC-W, Beltsville, MD 20705. 3 International Center of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya. 4 Institute of Plant Diseases and Plant Protection, Leibniz Univer- sita ¨ t Hannover, Herrenhaeuser Str. 2, 30419 Hannover, Germany.