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Too bristly for a hoverfly, it is an early spring tachinid, a fly parasitic upon moth caterpillars. I am finding it commonly in heath/woods in the Vale of York at the moment, and have seen it in Dalby forest before, too.
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Keep looking - we could do with some more "dots" on the map for the Yorkshire area. The Tachinid Recording Scheme dataset on the NBN was updated last month, so see the NBN link for a map - lots of blank space.
Tachinid Recording Scheme
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I don't know what the expected abundance would be for Tachina ursina, but it has been very abundant at my local site, the last two weeks. Allerthorpe Common is conifer plantation over lowland heath (though that is virtually all gone). I have been seeing 50+ every day for a couple of weeks, now. I started counting them one day, along one of the tracks, but stopped when I got to 50 in the space of the same number of yards. They were basking on grass at the sunny side of a track at about 09.30hrs, just as the sun came up over the trees opposite. The overall number seen that day is hard to estimate, but would be well over 200. To me, that seemed like a huge number for a tachinid fly?
Tachina ursina is one of those species where we still do not know the host or hosts. Going by the numbers reportedm its likely to be something fairly common. A good host population can support a good parasite population, something like Eriothrix rufomaculata can be couned in the thousands in a large grassy meadow in summer.
Lat/Lng: 54.25452, -0.69437
OS grid ref: SE851851