Nutritional benefits of intraguild predation and cannibalism among generalist and specialist phytoseiid mites

1. Intraguild predation and cannibalism are common among predaceous phytose iid mites (Acari, Phytoseiidae) but the nutritional benefits gained by thes e processes are poorly understood. 2. The study reported here addressed the questions of whether cannibalism a nd intraguild predation provide different nutritional benefits and whether the ability to utilise cannibalism and intraguild predation is linked to th e diet specialisation of phytoseiid mites. Specialists tested were Phytosei ulus macropilis, Galendromus occidentalis, and Neoseiulus longispinosus; ge neralists tested were Amblyseius andersoni, Neoseiulus cucumeris, and Neose iulus fallacis. 3. All generalists and the specialist P. macropilis were able to complete j uvenile development with both con- and hetero-specific prey. Juvenile devel opment of generalists was shorter with heterospecific prey than with conspe cific prey, whereas development of the specialist P. macropilis did not dif fer between prey types. Only a few N. longispinosus and G. occidentalis, bo th specialists, reached adulthood by cannibalism but none reached adulthood by intraguild predation. 4. All generalists were able to sustain oviposition by intraguild predation . Neoseiulus cucumeris and A. andersoni laid more eggs with heterospecific prey than with conspecific prey, whereas N. fallacis had similar ovipositio n rates with both prey types. No specialist sustained oviposition by intrag uild predation or cannibalism. 5. Overall, generalists gained equal or more nutritional benefits by intrag uild predation than by cannibalism and were able to utilise phytoseiid intr aguild prey as an alternative food source. Specialists gained equal or more nutritional benefits from cannibalism than from intraguild predation. For specialists, con- and hetero-specific phytoseiids may be considered only a supplemental food.