Predation by <i>Ostenia robusta</i> on <i>Costelytra zealandica</i> pupae

Abstract

Soil sampling in a cereal crop near Southbridge Canterbury revealed dipteran larvae attacking Costelytra zealandica (White) pupae Approximately 50 of the pupae had larvae associated with them DNA sequencing analysis of larval specimens indicated they most likely belonged to the family Dolichopodidae Larval specimens were reared through to adults and were identified as Ostenia robusta (Hutton) (Diptera Dolichopodidae) This is the first record of the association of O robusta larvae with C zealandica pupae A general description of the adult and larva of this species is provided along with DNA sequencing data and observations on its association with C zealandica pupae The potential role of O robusta in regulating populations of C zealandica is briefly considered

Biology of <i>Ostenia robusta</i> observations on life history and behaviour

“…The most likely explanation is the prey items offered were not suitable but it is possible that O. robusta does not feed as an adult. There is also no positive evidence about the conditions required for oviposition (Chynoweth et al 2013) and again in 2013, but none of the few O. robusta larvae found in 2014 were associated with C. zealandica and no such association has been detected elsewhere when C. zealandica pupae were collected for other purposes (R.J. Townsend, personal observation). It is possible that the association between these O. robusta and C. zealandica was coincidental and does not reflect the usual diet of O. robusta.…”

“…All O. robusta adults and larvae were collected from the same farm at Southbridge, Canterbury (43°49.061S; 172°14.445E), where predation on C. zealandica was first observed (Chynoweth et al 2013). Collections were made across several adjacent paddocks from 2013-2015.…”

“…From 11 December 2013 to 7 March 2014 there were 16 sticky traps placed in one field of clover (2 traps) and two adjacent wheat fields (3 traps in one field, 11 traps in the other). For this first season the trap locations targeted areas where O. robusta larvae had been found in 2012 (Chynoweth et al 2013). From 1 December 2014 to 7 April 2015 there were 16 sticky traps placed across one field of radish (4 traps), one ryegrass field (6 traps) and two adjacent wheat fields (2 traps in one, 4 in the other).…”

“…Ostenia robusta (Hutton) (Diptera: Dolichopodidae) is endemic to New Zealand and has been recorded from both the North and South Islands (Bickel 1991;Chynoweth et al 2013). In 2012 a population of O. robusta larvae was discovered at a farm in Southbridge, Canterbury, feeding on pupae of Costelytra zealandica (White) (Coleoptera: Scarabaeidae) (Chynoweth et al 2013). Various pathogens, parasitoids and predators are known to attack grass grub, C. zealandica (Cameron & Wigley 1989), but O. robusta was not recorded as a predator of C. zealandica before 2012.…”

“…Larvae are generally found in moist habitats such as damp soil, leaf litter or rotting wood (Daly et al 1998) with some species wholly aquatic at the larval stage (Reeves et al 2004;Hernandez 2008). Chynoweth et al (2013) presented the first information about the life history of O. robusta. The present study follows directly from that previous work to document adult emergence over two summers and to present observations on feeding and reproductive behaviour.…”