Relative abundance and seasonality of calliphoridae and sarcophagidae (diptera), potential vectors of rabbit haemorrhagic disease virus (rhdv) in the south island of new zealand

Abstract

In rabbit-prone areas of the South Island of New Zealand, a field survey was undertaken of the incidence, relative abundance and seasonality of possible rabbit haemorrhagic disease virus (RHDV) vectors, blowflies (Diptera: Calliphoridae) and fleshflies (Diptera: Sarcophagidae). Flies were trapped over a 4-day period each month for a year except during the winter months. Liver-baited Western Australian fly traps were set in Marlborough (three sites), the Mackenzie Basin (three sites) and Central Otago (six sites). Eight species of calliphorids (blowflies) and the sarcophagid (fleshfly), Hybopygia varia (Walker) were trapped. Numbers were generally higher at shrubby or grassy sites compared with bare open sites with little vegetation. More H. varia were trapped at sites grazed by cattle than at other sites. In March and November 1999, and January 2000, sticky traps attached to cages containing either a dead, live, or no rabbit were set up at two of the Central Otago sites where rabbit control had been poor (Sugar Loaf), and good (Locharburn), respectively. Blowflies were more abundant on sticky traps at the Locharburn site than at Sugar Loaf. Both groups of flies were attracted in significantly greater numbers to dead rabbits compared with live rabbits and empty cages. No evidence of RHDV was found on flies from either site, on any of the three dates. The implications of these results are discussed in the context of rabbit biological control.