Flight tube and field cage studies of harmonic radar tagged Bactrocera dorsalis and Ceratitis capitata (Diptera, Tephritidae): effects of tag size, sex, rearing, and irradiation.

Abstract

Tracking individual insects with harmonic radar (HR) allows observations of insect movement behavior under wild and semi-wild conditions. However, attaching tags to insects has the potential to alter natural behavior. Quantifying the negative effects of tag attachment may allow researchers to correct movement parameters to account for deviations from natural movements, thus producing more accurate estimates of insect behavior. Using two HR tag sizes, ~350 (small) and ~570 μg (large), the movements of Ceratitis capitata and Bactrocera dorsalis were investigated in flight tubes and an outdoor field cage. Bactrocera dorsalis with small tags attached did not perform differently than untagged flies in flight tubes, while flies with large tags took longer to exit the tubes. Time to exit did not vary with B. dorsalis body size, wing area, or wing length for any tagged status (untagged, small, or large). However, B. dorsalis exit times did vary with rearing and irradiation status but not with sex. For C. capitata, negative impacts were observed on both the time to exit and the failure to exit rate. Field cage experiments revealed differences in movement parameters among tested groups. For instance, female, colony-reared, non-irradiated, B. dorsalis showed the greatest bias in (pseudo) turning angles; male, wild, non-irradiated, B. dorsalis showed the weakest correlation between flight and wind direction (β); and colony-reared C. capitata showed random movement directions (other groups showed directional biases). This study shows the feasibility of tracking tephritids as small as C. capitata and demonstrates the advantages of using the smallest possible tags.