Effects of conspecific and heterospecific competitors on feeding and oviposition of a predatory ladybird: a laboratory study

There are several examples of intraguild interactions among insect predators of aphids, but little is known regarding the effects of interactions on feeding and oviposition of individual competitors in a guild. In the laboratory, we determined the feeding and oviposition responses of a ladybird predator to its conspecific and heterospecific competitors in an aphidophagous guild. Gravid females of Menochilus sexmaculatus ( Fabricius) ( Coleoptera, Coccinellidae) reduced oviposition, but not feeding, when exposed to immobilised conspecific or Coccinella transversalis ( Fabricius) ( Coleoptera, Coccinellidae) individuals in the short-term ( 3 h) and long-term ( 24 h). Feeding and oviposition responses were not affected when M. sexmaculatus females were exposed to larvae or adults of Scymnus pyrocheilus Mulsant ( Coleoptera, Coccinellidae) beetles or larvae of the syrphid fly Ischiodon scutellaris ( Fabricius) ( Diptera: Syrphidae). The ratio of eggs laid to numbers of aphids consumed by M. sexmaculatus females was also affected by the presence of conspecific or C. transversalis larvae. The results suggest that fecundity of this predator may be affected by both conspecific and heterospecific competitors in a patchy resource.