Comparison of chemosensilla in three phytoseiid mites with different feeding habits

Abstract Phytoseiidae comprised over 2000 described species with different feeding habits. However, the mechanisms of food selection were virtually unknown in most phytoseiid mites. To explore the potential mechanism of odor perception, we compared the type and number of chemosensilla on the tarsi of legs and pedipalps by scanning and transmission electron microscopy in three representative predatory mites, i.e., Phytoseiulus persimilis (specialized predator of Tetranychus), Neoseiulus californicus (selective predator of tetranychid mites), and Amblyseius swirskii (generalist predator). All three species had two types of putatively olfactory sensilla, with a porous vs. grooved surface on the tip of the first pair of legs. Of these, five porous setae were found in each of the three species of predatory mites studied. However, only one grooved seta was found at the tip of the first pair of legs in P. persimilis, and two in A. swirskii and N. californicus. In addition, the pedipalp has nine grooved setae, which were hypothesized to be contact chemosensilla in each of the three species. No porous setae were found on either pedipalp or the other three pairs of legs, i.e., leg II, III and IV. Additionally, we provided a new chaetotactic notation for the tarsus of leg I by considering the type and number of setae based on our observation of the three species of Phytoseiidae studied.