Readdressing methods for evaluating New World screwworm (Diptera: Calliphoridae) strain performance

Authors: Arp, Alex; RUND, SAMUEL - Notre Dame; VASQUEZ, MARIO - US Department Of State; QUINTERO, GLADYS - US Department Of State; SAGEL, AGUSTIN - US Department Of State; Hickner, Paul

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2026
Publication Date: 9/20/2026
Citation: Arp, A.P., Rund, S.S., Vasquez, M., Quintero, G., Sagel, A., Hickner, P.V. 2026. Readdressing methods for evaluating New World screwworm (Diptera: Calliphoridae) strain performance. Journal of Economic Entomology. https://doi.org/10.1093/jee/toag281.
DOI: https://doi.org/10.1093/jee/toag281

Interpretive Summary: A primary component of control and eradication of the New World screwworm is the release of millions of sterile flies which mate with wild populations resulting in infertility and population reduction, called sterile insect technique (SIT). For SIT to be effective, the sterile males need to be competitive with wild males and successful at mating wild females. Sterile flies undergo many quality control checks to ensure they are healthy, but often these tests are not a good proxy for actual behavior in the field or they may be unable to detect differences that can impact field performance. To address this, we evaluated mating behavior using a larger arena and looked at correlations with physical traits. We found that although both strains had similar physical traits, one was much more successful at mating. We also used electronic monitoring devices to evaluate behavior. A locomotor activity monitor that characterizes daily behavior over long periods of time found that wild lines were no different from production strains, giving confidence that there are no discrepancies in daily activity patterns. Flight recording devices were also developed which can accurately evaluate flight performance between strains and were able to identify differences between strains. Overall, these new tests were more accurate at determining strain health and mating capabilities than previously used metrics and will serve as excellent tools for sterile screwworm release programs.

Technical Abstract: For the sterile insect technique to successfully control New World Screwworm (NWS), Cochliomyia hominivorax Coquerel, 1858, released sterile males must be healthy and reproductively competitive with wild populations. In mass-rearing, daily evaluations of developmental metrics are used to evaluate production efficiency, output, and to identify problems with production processes. These observations can detect major strain or production issues, but they may not be sufficient to evaluate how a strain will perform in the field. Here, we evaluate novel mating assays, locomotor activity monitors (LAMs), and flight mills to assess strain performance. Standard production parameters and a non-competitive mating assay were unable to identify differences between outbreak-based production strains and production strains. When placed in open-choice mating tests, the outbreak strain mated with nearly double the number of females as the production strain, implying production males may have reduced mating success when used in sterile releases. No significant differences were observed in the temporal (‘circadian’) locomotor activity between males, but outbreak strain females were more active than outbreak males and the previous production strain males and females. Flight mills found that the outbreak-based production strain flew farther on average than the previous production strain and showed that flight ability was not strongly correlated to fly physical parameters. Overall, our novel tests were able to detect differences in strain quality that were not apparent in the physical measurements or tests typically used to evaluate strains in production.