Life history trade-offs of Orius insidiosus (Say) (Hemiptera: Anthocoridae) under artificial lights

In recent times, adoption of artificial lights for improved protected crop production has trended as a global phenomenon. Despite this, there remains a need to better grasp how these new environments will affect the diversity of beneficial and pest arthropods either deliberately or inadvertently present on crops, including the anthocorid bug, Orius insidiousus (Say) a key predator of thrips and other economically important pests. For this species, there is still routine failure of its biocontrol programmes under short season conditions and under artificial lights, which this study aims to better understand why. In this context, O. insidiosus was examined for its response to each of seven distinct environmental conditions that include lights of different types (LED, HPS and fluorescence), at different intensities (12.4 – 381.8 μmoles/m2/s), of varying spectral compositions (white, red-630nm, blue-458nm), and applied for varying photoperiods (8 - 20h/day) as well as their interaction with temperature. To this end, we measured and compared under each of these treatments; O. insidiosus egg and nymphal development time, nymphal and adult longevity, female fecundity, length of pre-, post-, and reproductive periods. Overall, individuals under a simulated summer condition (381.8 μmoles/m2/s white fluorescent light; 16 h/day; 24°C) had the shortest egg and nymphal development periods and the highest rate of daily egg laying, but also the highest proportion (27%) of non-reproductive females, the lowest total offspring production and the shortest adult lifespans. This suggests predators under this condition adopt an R-selective strategy, which may be acceptable when the bug is regularly re-introduced. Among remaining treatments, two distinct reproductive strategies appeared; one formed by the four LED treatments, characterized by a high total number of offspring produced per female at a relatively high rate and over a sustained period of time. Interestingly, under the low intensity blue LED treatment (12.4 μmoles/m2/s; 20h; 20°C), 100% of females tested were reproductive, which may indicate the particular value of even small amounts of short wavelength light for activating population growth. A third reproductive strategy appeared for O. insidiosus under simulated winter and HPS conditions, characterized by the lowest rates of daily egg production but the longest of all reproductive periods measured in this study. Such distinct reproductive strategies indicate the considerable plasticity of O. insidiosus life history faced with varying environments, and support the value of altering conditions in protected crops to optimize predator performance, which is further discussed.