title: Eggs of Mallada desjardinsi (Neuroptera: Chrysopidae) are protected by ants: the role of egg stalks in ant-tended aphid colonies.
abstract: In ant-aphid mutualisms, ants usually attack and exclude enemies of aphids. However, larvae of the green lacewing Mallada desjardinsi (Navas) prey on ant-tended aphids without being excluded by ants; these larvae protect themselves from ants by carrying aphid carcasses on their backs. Eggs of M. desjardinsi laid at the tips of stalks have also been observed in ant-tended aphid colonies in the field. Here, we examined whether the egg stalks of M. desjardinsi protect the eggs from ants and predators. When exposed to ants, almost all eggs with intact stalks were untouched, whereas 50-80% of eggs in which stalks had been severed at their bases were destroyed by ants. In contrast, most eggs were preyed upon by larvae of the lacewing Chrysoperla nipponensis (Okamoto), an intraguild predator of M. desjardinsi, regardless of whether their stalks had been severed. These findings suggest that egg stalks provide protection from ants but not from C. nipponensis larvae. To test whether M. desjardinsi eggs are protected from predators by aphid-tending ants, we introduced C. nipponensis larvae onto plants colonized by ant-tended aphids. A significantly greater number of eggs survived in the presence of ants because aphid-tending ants excluded larvae of C. nipponensis. This finding indicates that M. desjardinsi eggs are indirectly protected from predators by ants in ant-tended aphid colonies.
authors.affiliation: Laboratory of Applied Entomology, Graduate School of Horticulture, Chiba University, 648 Matsudo, Chiba.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hayashi
authors.forename: Masashi
authors.initials: M
authors.lastname: Nomura
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology; D001042:Aphids / Q000502:physiology; D007313:Insecta / Q000254:growth & development / Q000502:physiology*; D007814:Larva / Q000502:physiology; D011235:Predatory Behavior; D013559:Symbiosis