The biology of the sheep blowflies Lucilia caesar and Lucilia sericata (Diptera: Calliphoridae) in relation to their control by trapping
This study was an investigation of aspects of the biology of sheep blowflies in relation to their control by trapping. In order to determine the species composition of blowfly larvae in ovine analysis cases in Scotland, samples of dipteran larvae were collected from live sheep throughout Scotland, reared in the laboratory, and identified once adult flies emerged. Lucilia sericata was found in 77% of samples, and other species in 49%. The most common alternative species were L. caesar, which occurred in 31% of samples, and Protophormia terraenovae, which occurred in 18%. Three other calliphorid species, Calliphora vomitoria, C. vicina, and L. illustris, and the muscid Muscina pabulorum were also found. The proportion of samples containing alternative species was significantly lower in eastern Scotland than in western Scotland. Significantly higher proportions of samples containing alternative species were collected at altitudes of 200 metres and above; from sheep of hills breeds; from rough grazing conditions and moorland; in the absence of trees; and in the presence of bracken. The importance of Lucilia caesar in myiasis cases in Scotland having been confirmed, the capture of this species was investigated using four different trap designs, all baited with beef liver and sodium sulphide solution. A horizontal target coated with a polybutene-based adhesive performed significantly better than a similar vertical target. Both of these adhesive designs demonstrated significantly higher catches of both male and female flies than a water trap and a commercially-produced enclosed trap, Fly City (P < 0.05). Subsequent investigations showed that catches on adhesive targets were significantly greater at a height of 0.2m than at ground level (P < 0.05), 0.6m, or 0.8m (P < 0.01). Catches were also increased on larger targets (P < 0.05), but there was no significant increase in catch per unit area with target size.