On the Food-habits of Some Aphidophagous Syrphid Larvae II

In this account a record is given of the food-habits of 12 species of aphidophagous Syrphidae commonly found in crop fields in Nagasaki. Food lists of Ischiodon scutellaris FABR., Paragus quadrifasciatus MEIG., P. tibialis FALLEN, Sphaerophoria cylindrica SAY, Sph, javana WIED., Syrphus torvus O.S. and Epistrophe aino MATS., with notes of their attacking dates of plant-lice, are given. Those of Syrphus ribesii L., S. serarius WIED., S. bilineatus MATS., Metasyrphus corollae FABR., and Epistrophe balteatus DE GEER were previously published by the writer in 1956. The plant-lice attacked by the 12 syrphids amount to 40 species, which belong to 20 genera, Aphis, Macrosiphum, Amphorophora, Capitophorus, Myzus, Rhopalosiphum, Hyalopterus, Macrosiphoniella, Brevicoryne, Phorodon, Pseudocerosipha, Megoura, Acyrthosiphum, Glyphina, Neophillaphis, Periphyllus, Prociphilus, Eulachnus, Lachnus, and Oregma, about 83 per cent of which belong to the tribe Aphidini of the Aphididae, being parasitic on 65 species of plants including common crops. Among these syrphids, Epistrophe balteatus may rank first in attacking as many as 37 species of plant-lice, while Syrphus torvus and Epistrophe aino may be the lowest ranking on the list, devouring merely 4 species of aphids respectively. The nonconcentricity of aphidophagous capacity is also discussed. With regard to to the aphidophagous capacity of syrphids, single aphidophagous capacity may be distinguished from complex aphidophagous capacity, the former consisting of any single species of syrphids and the latter being composed of more than two species of them. Because of their simultaneous employment of single aphidophagous capacity in the destruction of the same or different plant-lice on different kinds of plants, the aphidophagous capacity of syrphids can not be exclusively concentrated on the destruction of a spefcific plant-lice on a specific crop during the same season. Complex aphidophagous capacity, in the same way, can not be exclusively concentrated upon the control of a specific aphid on a specific plant. In other words, during the same season, any single or complex aphidophagous capacity employed in the destruction of a specific aphid on a specific crop may simultaneously be dispersed toward the same or different aphids on different plants.