Mast seeding of Chionochloa (Poaceae) and pre-dispersal seed predation by a specialist fly (Diplotoxa, Diptera: Chloropidae)

Abstract Levels of seed predation were recorded between 1986 and 1992 in Chionochloa pattens, C. oreophila, C. flavescens, C. macra, and C. crassiuscula populations at various altitudes at three sites in Canterbury. There were consistently high levels of attack by a chloropid fly, Diplotoxa similis: between 22 and 94% of florets showed evidence of fly damage, except at higher altitudes (decreasing to 2% in C. pattens at 1620 m) and in C. oreophila (6 – 10%). Since D. similis emerges rapidly from the pupa and since larvae possibly move between florets, the number of insects found underestimated the number of florets predated by up to 90%. Seed set varied from 2% to 59% and was negatively correlated with seed predation. Two other Chionochloa seed predators have been reported previously: a moth, Megacraspedus calamogonus, and an unidentified cecidomyiid (gall midge) larva. In this study, larvae similar to Megacraspedus were very rare, and we suggest that the unidentified cecidomyiid is actually a misidentifi...