Intraguild predation by the predatory soil mite Blattisocius mali (Acari: Blattisociidae) and its predation preference towards conspecific and heterospecific prey

The predatory soil mites Blattisocius mali and Stratiolaelaps scimitus share similar prey and occupy similar habitats. This study explores intraguild predation (IGP) by various life stages of B. mali on the developmental stages of S. scimitus across different starvation periods, and their predation preference for conspecific and heterospecific eggs or larvae in the absence of shared prey at 25 °C, 85 ± 5% RH, and a 16 L:8D photoperiod. All feeding developmental stages of B. mali consumed S. scimitus eggs and larvae; however, they did not kill S. scimitus deutonymphs or later developmental stages. Few B. mali females killed S. scimitus protonymphs, whereas other developmental stages of B. mali did not kill these protonymphs. Interestingly, the propensity of B. mali females to eat heterospecific eggs was not affected by the starvation period. However, their predation on heterospecific larvae increased with increasing starvation period up to 48 h and then stabilized. Blattisocius mali females, males, or deutonymphs showed a greater propensity towards heterospecific larvae compared to eggs across all the tested starvation periods. Notably, the proportion of B. mali protonymphs that ate heterospecific eggs was significantly higher than that of other stages, and males had a significantly greater tendency to prey on heterospecific larvae relative to other stages. When given a choice, all life stages of B. mali clearly distinguished between conspecific and heterospecific eggs, preferring to prey on conspecific eggs. In contrast, when selecting between conspecific and heterospecific larvae, they preferred to prey upon heterospecific larvae. This study suggests that B. mali may interact with S. scimitus and feed on their eggs and larvae. Further studies are necessary to investigate the effect of IGP between B. mali and S. scimitus on their survival, reproduction, population dynamics, and ultimately pest suppression.