Temporal trends: phase-shifted time-series analysis reveals highly correlated reproductive behaviors in <i>Hermetia illucens</i> (Diptera: Stratiomyidae)

For those researching reproduction of the black soldier fly (BSF), finding meaningful correlations between mating and downstream reproductive fitness metrics, owing to complex reproductive behavior and physiology, has been challenging. On the one hand, mating is not necessarily deterministic of fertile eggs being produced, since females might lay unfertile eggs both before and after mating. But conversely, the process is not "random" either, since fertility is predicated on the exchange of gametes during mating. To investigate the relationship between mating and other reproductive metrics, a cross-correlation analysis between lagged time series was conducted on data previously collected during a semi-outdoor greenhouse experiment. This process compared the average percent correlation between un-lagged mating with oviposition in traps, oviposition outside traps, total weight of eggs deposited, and hatch rate, which were lagged n = 0 to n = 6 days. This revealed that average mating was 97.54% correlated with oviposition in traps lagged by n = 2 days. For oviposition outside of traps, total egg weights, and hatch rate, these were also ∼71.63% correlated, 60.29% correlated, and 75.16% correlated with mating, respectively, which were optimized when the time series were lagged n = 3 days. These trends likely have a biological basis since flies decrease their reproductive activity as they expend energy and senesce, aligning with temporal patterns consistently observed during BSF rearing.