First host record of Argyresthia assimilis Moriuti, 1977 (Lepidoptera: Yponomeutidae) and a description of its annual life history

Abstract

Seed predation by insects is an important factor influencing the evolution of synchronized annual fluctuations in the seed production of plant species. Photinia glabra (Rosaceae) is an evergreen bird-dispersed tree species that exhibits high variation in annual fruit production and heavy seed predation by insects. To identify the insect species infesting P. glabra, and to investigate seed predation patterns by these insects, we periodically sampled its infructescences from post-flowering until fruit ripening. We reared insects obtained from infested P. glabra fruits, and found that the insect species was Argyresthia assimilis Moriuti, 1977 (Lepidoptera: Yponomeutidae), whose host plant has been unknown since it was first described. Emerging females oviposited on P. glabra fruits in late September, usually laying a single egg per fruit. Larvae bored into the oviposited fruits and fed on seeds within the fruit. Final instar larvae exited the fruits to form cocoons in advance of fruit ripening in late December. Because P. glabra decreases the number of fruits after flowering (mid-May to mid-August), and because ripe fruits are heavily eaten by birds, immature life history of A. assimilis prevents egg loss by laying eggs after the decline in fruit number, and enables larvae to avoid bird predation within ripe fruits. This tight synchronization between insect and host plant life histories suggests that the host range of A. assimilis is restricted to P. glabra and its close relatives.