On the Number of Aphids Destroyed by Syrphid Larvae

1989

-The syrphid fly Episyrphus balteatus (de Geer) migrating from maple trees to leguminous plants in mid-April, assesses the qualitative and quantitative value of pea aphid colonies for securing successful development of her offspring. She selects young and "promising" pea aphid colonies of small size. This generally agrees with the "buy-futures" ovipositional tactic the syrphid fly adopts when it utilizes the maple aphids. The advantage of a "buy-futures" ovipositional tactic found in many syrphid species is discussed in comparison with other aphidophagous insects.Episyrphus balteatus (de Geer) is a member of the "aphidozetic" syrphids (Chandler 1968a) and the female of this species lays her eggs adjacent to aphid colonies. In Kyoto, E. balteatus females actively visit the Japanese maple, Acer palmatum Thunb., in early spring and oviposit near the colonies of 2 species of maple aphid, Periphyllus californiensis (Shinji) and Yamatocallis tokyoensis (Takahashi). When doing so, they show no preference between these2 species.The value of maple aphid colonies as a food resource for .fly larvae changes with the progress of colony development. From previous results (Kan 1988a), it was made clear that E. balteatus females, in search of oviposition sites, are assessing the qualitative and quantitative value of maple aphid colonies for securing the successful development of their offspring. E. balteatus females, select small, young and "promising" maple aphid colonies consisting of nymphs and/or fundatrices as their oviposition sites, and neglect large, older ones including winged adults. It was also indicated that such a "buy-futures" tactic will benefit the offspring of E. balteatus in finding suitable and sufficient food.In mid-April, when E. balteatus eggs are no longer found on maple trees, heavily infested with maple aphids, eggs are often seen at small, young colonies of other species of aphids, mainly pea aphid colonies on the leguminous plant (vetch), In the present study, the ovipositional tactic of E. balteatus with these 3 pea aphid species was investigated in order to clarify whether or not this syrphid species adopts different ovipositional tactics when the prey aphid species is different. Materials and Methods

Section: Discussionmentioning

confidence: 99%

Assessment of aphid colonies by hoverflies. III Pea aphids andEpisyrphus balteatus (de Geer) (Diptera: Syrphidae)

1989

“…Ninomiya (1957a) has pointed out the tendency for E. balteatus larvae to prefer aphid nymphs to adult aphids as their diet. The adult aphid is much larger than the lst-instar fly larva and with a hard body surface.…”

Section: Discussionmentioning

confidence: 99%

Assessment of aphid colonies by hoverflies. I maple aphids andEpisyrphus balteatus (de Geer) (Diptera: Syrphidae)

1988

In the syrphid hoverfly Episyrphus balteatus (de Geer), females in search of oviposition sites are assessing the qualitative and quantitative value of aphid colonies for securing the successful development of their offspring. They select small, young and "promising" aphid colonies consisting of nymphs and/or fundatrices as their oviposition sites, and neglect large, older ones including winged adults. Such "buy-futures" tactics will benefit the offspring in finding suitable and sufficient food.

“…The adult aphid with a hard body surface is much larger than the 1 st-instar larva of the 3 syrphid species. Ninomiya (1957a) has pointed out the tendency for fly larvae of E. balteatus and 2 other syrphid species to prefer aphid nymphs to adult aphids as food, irrespective of the difference in aphid species. Such a tendency may also be found in In the field, however, older larvae of the 3 syrphid species are observed actively migrating among pea plants, After having consumed all the aphids in a colony, the larva migrates, searching for another aphid colony to attack.…”

Section: Discussionmentioning

confidence: 99%

Assessment of aphid colonies by hoverflies. II pea aphids and 3 syrphid species;Betasyrphus serarius (Wiedemann),Metasyrphus frequens Matsumura andSyrphus vitripennis (Meigen) (Diptera: Syrphidae)

1988

Abstract-In the aphidophagous syrphid species, Betasyrphus serarius (Wiedemann), Metasyrphus frequens Matsumura and Syrphus vitripennis (Meigen), females in search of oviposition sites assess the qualitative and quantitative value of pea aphid colonies for securing the successful development of their offspring. They select, as their oviposition sites, young and "promising" aphid colonies consisting of nymphs and/or adult aphids including few winged adults. They neglect large, older colonies of 4th-instar nymphs and/or winged adult aphids. The 3 syrphid species adopt "buy-futures" ovipositional tactic as does Episyrphus balteatus (de Geer), although some tinge of "spot-transaction" is noticed in M. frequens and S. vitripennis.Aphid colonies are the only food resources for aphidophagous syrphid larvae. Aphidophagous syrphid flies often lay their eggs in or close to aphid colonies (Bombosch 1962(Bombosch , 1963Volk 1964;Chandler 1965;Schneider 1969). The resource value of the aphid colony changes with the progress of its development. It is therefore likely that female flies in search of oviposition sites are assessing the qualitative and quantitative value of aphid colonies for securing the successful development of their offspring.A previous study demonstrated that female flies of Episyrphus balteatus (de Geer) select small, young, and "promising" colonies of maple aphids as their oviposition sites and neglect large, older colonies. Such a "buy-futures" tactic appears to benefit the offspring in finding suitable and sufficient food (Kan 1988).After the ovipositional peak of E. balteatus The mode of colony development in these syrphid species appeared to be different from that of the maple aphids. The ovipositional tactics of B. serarius, M. frequens and S. vitripennis, predominantly directed toward the pea plant, were therefore investigated.