New species ofResseliella(Diptera: Cecidomyiidae), injurious toDianellaandPhormium(Xanthorrhoeaceae) in Australia and New Zealand

Abstract

Larvae of an undescribed gall midge species were found feeding within leaf sheaths and between leaves of potted plants of flax lilies Dianella revoluta, D. tasmanica, D. caerulea (all native to Australia) and New Zealand flax Phormium tenax (native to New Zealand) in South Australia. The larvae were previously recorded infesting Phormium tenax in New Zealand. The new species is described and named Resseliella xanthorrhoeae Kolesik. Larvae, pink when young and red when mature, feed gregariously, causing extensive tissue necrosis. Pupation takes place in the soil. Large necrotic areas remain visible after the fully grown larvae exit the sheaths until the end of the infested leaves’ life, temporarily decreasing ornamental value of the plants. Infested plants recover from the injury by shedding off infested leaves and producing fresh leaves. The new species is the first Resseliella Seitner reported from Australia and New Zealand and the first species of this genus known to infest plants from the family Xanthorrhoeaceae.