Evolutionary and ecological transitions from carnivorous to omnivorous feeding may be constrained by the ability of the animal to cope with disparate types of foods, even if preadaptations for such behaviour exist. The omnivorous true bug, Dicyphus hesperus (Hemiptera: Miridae) requires both animals (small, soft-bodied insects) and plants in its diet and obtains the majority of its dietary and metabolic water from plant feeding. Serrations on the lateral margins of the mandibular stylets wear with age, and this wear is exacerbated when the insects feed on plants compared to those provided free water and no plants. D. hesperus that feed on plants attack fewer prey but consumed similar amounts of prey tissue compared to individuals that were provided free water. Although others have shown mandible wear for plant-chewing animals we show for the first time that plant feeding can impose similar wear on plant-piercing animals as well.

The effects of intraguild interactions between Dicyphus hesperus Knight (Hemiptera: Miridae) and Paecilomyces fumosoroseus Apopka-97 (PFR-97 TM ) (Wize) Brown and Smith (Ascomycota: Hypocreales) on Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) populations were investigated in tomato greenhouse microcosms. Conditions were established in which interference or synergy would most likely occur; namely, a high number of available whiteflies were combined with large numbers of both D. hesperus and PFR-97 TM . We measured live whitefly density in a factorial repeated measures experiment where plants were provided or withheld releases of D. hesperus and/or applications of PFR-97 TM for 6 weeks. Releases of D. hesperus were made at a rate of 10 adults/plant during the first and third week and PFR-97 TM suspensions were applied with a backpack sprayer at a rate of 18 Â 10 7 , 1.3 Â 10 7 and 1.2 Â 10 7 viable blastospores/ml during the first, third and fourth week, respectively. Results revealed a non-significant interaction effect between D. hesperus and PFR-97 TM , indicating that their actions were independent. Individual whitefly reductions of 48% and 35% were achieved by PFR-97 TM and D. hesperus, respectively. Collectively, the natural enemies reduced whitefly densities by 62% relative to the controls. The density of D. hesperus adults was unaffected by multiple applications of PFR-97 TM . These results suggest that the combination of generalist entomopathogenic fungi and generalist predators has the potential to cause increased pest mortality despite evidence of minimal interference.

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