Predator guilds attacking coccinellid eggs vary among egg mass species and across foraging habitats

The establishment and spread of exotic coccinellids coincides with the decline of native coccinellids. Due to this observation, intraguild predation by exotic coccinellids on native coccinellid eggs was proposed as a mechanism for the decline. The objectives of this study were to determine if exotic coccinellids were dominant predators of native lady beetle egg masses and to document the guild of predators that attack coccinellid egg masses within crop and semi-natural habitats. Video experiments revealed that exotic coccinellids were not dominant predators of coccinellid egg masses but did show a diverse guild of predators which included Stylommatophora, Opiliones, Oniscidea, Coccinellidae, Gryllidae, Neuroptera, Tettigoniidae, Acrididae, Formicidae, Nabidae, Thripidae, Syrphidae, Araneae, Staphylinidae, and Diplopoda. This predator guild varied across habitats, with the greatest diversity found within semi-natural grassland habitats and a lesser diversity in alfalfa and soybean habitats. Redundancy analysis revealed that two primary egg predators maintained a consistent pattern of predation across both 2010 and 2011: Formicidae and Oniscidea. Formicidae were positively correlated with predation on H. axyridis egg masses, while Oniscidea was positively correlated with predation on H. convergens egg masses. These findings have indicated that exotic lady beetles are not a significant predator of native coccinellid egg masses, but that there is a diverse predator guild. In addition, alfalfa may be an important habitat for the conservation of native lady beetles due to reduced egg predation.