Species composition and larval habitats of blowfly (Calliphoridae) populations in upland areas in England and Wales.

1. Bait trapping at upland sites in England and Wales, mainly at 400-700 m altitude, showed that Calliphora vomitoria L. usually outnumbered all other blowflies. C.vicina R.-D., C.loewi End. and C.alpina Zett were usually present in much lower numbers, with the last-named occurring at north Pennine sites, but being replaced by C.subalpina Ringd. at a south Pennine (Peak District) and a Welsh site. Catches normally included Cynomya mortuorum L., and Phormia terraenovae R.-D. was present at about half of the sites, usually in low numbers. 2. Lucilia spp. (predominantly L.caesar L.) were often abundant in catches at 300-430 m, but were absent or rare at 500 m and above, except at certain times. 3. Exposure of mouse carcasses at north Pennine upland sites, and rearing of adults from them, showed that they were colonized in a very indeterminate variable way by C.vicina, C.loewi, C.alpina and Cy.mortuorum, with dominant and subsidiary species varying in identity and numbers within periods as short as 3 weeks. 4. Sampling of large carcasses, i.e. hill sheep casualties in Co. Durham, showed that C.vomitoria predominated as the blowfly colonist, with C.vicina and Cy.mortuorum in much smaller numbers.