The effects of colony age and Wolbachia as they relate to quality and fitness of Spalangia cameroni (Hymenoptera: Pteromalidae)

Spalangia cameroni is a commercially available pupal parasitoid of filth flies. Biological control using pupal parasitoids (Hymenoptera:Pteromalidae) is an alternative to chemical insecticides and a sustainable option for filth fly control in livestock operations.  Though pteromalid parasitoid sales are increasing, augmentative releases evaluated on cattle and poultry operations have had mixed results. Declines of control efficacy could be attributed to deterioration in laboratory reared insects. Physiological, behavioral and life history characteristics may be modified with the propagation of small cultures of insects in the lab. The mass rearing of pteromalids in the laboratory may reduce their fecundity and host searching ability when released in the field, not resulting in the desired pest control. Additionally, Wolbachia bacteria are known to infect S. cameroni and produces an incomplete form of cytoplasmic incompatibility.  Three colonies of S. cameroni all collected from the same dairy farm but different years were evaluated for changes in fitness including female longevity, fecundity and host-searching ability. Each colony was screened and subjected to phylogenetic analyses using wsp gene sequences. Significant declines in fecundity and female longevity were seen between the colony established in 2000 from the 2012 colony. The 2010 colony was lived the shorted period of time and produced the fewest offspring from either of the other two colonies, though was more efficient at searching and parasitizing puparia than the 2000 colony. Wolbachia screening identified multiple strains within each colony and two strains new to this species were identified. These results suggest that multiple methods for quality control must be used for laboratory reared insects. It is unknown to what extent Wolbachia plays in colony fitness, but different strains could play a part in changes to life history parameters.